Double 結構

定義

表示雙精度浮點數。Represents a double-precision floating-point number.

public value class Double : IComparable, IComparable<double>, IConvertible, IEquatable<double>, IFormattable
public value class Double : IComparable, IConvertible, IFormattable
public value class Double : IComparable, IComparable<double>, IEquatable<double>, IFormattable
public struct Double : IComparable, IComparable<double>, IConvertible, IEquatable<double>, IFormattable
[System.Serializable]
public struct Double : IComparable, IConvertible, IFormattable
[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public struct Double : IComparable, IComparable<double>, IConvertible, IEquatable<double>, IFormattable
public struct Double : IComparable, IComparable<double>, IEquatable<double>, IFormattable
type double = struct
    interface IConvertible
    interface IFormattable
[<System.Serializable>]
type double = struct
    interface IFormattable
    interface IConvertible
[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type double = struct
    interface IFormattable
    interface IConvertible
type double = struct
    interface IFormattable
Public Structure Double
Implements IComparable, IComparable(Of Double), IConvertible, IEquatable(Of Double), IFormattable
Public Structure Double
Implements IComparable, IConvertible, IFormattable
Public Structure Double
Implements IComparable, IComparable(Of Double), IEquatable(Of Double), IFormattable
繼承
Double
屬性
實作

範例

下列程式碼範例說明如何使用 DoubleThe following code example illustrates the use of Double:

// The Temperature class stores the temperature as a Double
// and delegates most of the functionality to the Double 
// implementation.
public ref class Temperature: public IComparable, public IFormattable
{
   // IComparable.CompareTo implementation.
public:
   virtual int CompareTo( Object^ obj )
   {
      if (obj == nullptr) return 1;
      
      if (dynamic_cast<Temperature^>(obj) )
      {
         Temperature^ temp = (Temperature^)(obj);
         return m_value.CompareTo( temp->m_value );
      }
      throw gcnew ArgumentException( "object is not a Temperature" );
   }

   // IFormattable.ToString implementation.
   virtual String^ ToString( String^ format, IFormatProvider^ provider )
   {
      if ( format != nullptr )
      {
         if ( format->Equals( "F" ) )
         {
            return String::Format( "{0}'F", this->Value.ToString() );
         }

         if ( format->Equals( "C" ) )
         {
            return String::Format( "{0}'C", this->Celsius.ToString() );
         }
      }
      return m_value.ToString( format, provider );
   }

   // Parses the temperature from a string in the form
   // [ws][sign]digits['F|'C][ws]
   static Temperature^ Parse( String^ s, NumberStyles styles, IFormatProvider^ provider )
   {
      Temperature^ temp = gcnew Temperature;

      if ( s->TrimEnd(nullptr)->EndsWith( "'F" ) )
      {
         temp->Value = Double::Parse( s->Remove( s->LastIndexOf( '\'' ), 2 ), styles, provider );
      }
      else
      if ( s->TrimEnd(nullptr)->EndsWith( "'C" ) )
      {
         temp->Celsius = Double::Parse( s->Remove( s->LastIndexOf( '\'' ), 2 ), styles, provider );
      }
      else
      {
         temp->Value = Double::Parse( s, styles, provider );
      }
      return temp;
   }

protected:
   double m_value;

public:
   property double Value 
   {
      double get()
      {
         return m_value;
      }

      void set( double value )
      {
         m_value = value;
      }
   }

   property double Celsius 
   {
      double get()
      {
         return (m_value - 32.0) / 1.8;
      }

      void set( double value )
      {
         m_value = 1.8 * value + 32.0;
      }
   }
};
// The Temperature class stores the temperature as a Double
// and delegates most of the functionality to the Double
// implementation.
public class Temperature : IComparable, IFormattable
{
    // IComparable.CompareTo implementation.
    public int CompareTo(object obj) {
        if (obj == null) return 1;

        Temperature temp = obj as Temperature;
        if (obj != null)
            return m_value.CompareTo(temp.m_value);
        else
            throw new ArgumentException("object is not a Temperature");	
    }

    // IFormattable.ToString implementation.
    public string ToString(string format, IFormatProvider provider) {
        if( format != null ) {
            if( format.Equals("F") ) {
                return String.Format("{0}'F", this.Value.ToString());
            }
            if( format.Equals("C") ) {
                return String.Format("{0}'C", this.Celsius.ToString());
            }
        }

        return m_value.ToString(format, provider);
    }

    // Parses the temperature from a string in the form
    // [ws][sign]digits['F|'C][ws]
    public static Temperature Parse(string s, NumberStyles styles, IFormatProvider provider) {
        Temperature temp = new Temperature();

        if( s.TrimEnd(null).EndsWith("'F") ) {
            temp.Value = Double.Parse( s.Remove(s.LastIndexOf('\''), 2), styles, provider);
        }
        else if( s.TrimEnd(null).EndsWith("'C") ) {
            temp.Celsius = Double.Parse( s.Remove(s.LastIndexOf('\''), 2), styles, provider);
        }
        else {
            temp.Value = Double.Parse(s, styles, provider);
        }

        return temp;
    }

    // The value holder
    protected double m_value;

    public double Value {
        get {
            return m_value;
        }
        set {
            m_value = value;
        }
    }

    public double Celsius {
        get {
            return (m_value-32.0)/1.8;
        }
        set {
            m_value = 1.8*value+32.0;
        }
    }
}
' Temperature class stores the value as Double
' and delegates most of the functionality 
' to the Double implementation.
Public Class Temperature
    Implements IComparable, IFormattable

    Public Overloads Function CompareTo(ByVal obj As Object) As Integer _
        Implements IComparable.CompareTo

        If TypeOf obj Is Temperature Then
            Dim temp As Temperature = CType(obj, Temperature)

            Return m_value.CompareTo(temp.m_value)
        End If

        Throw New ArgumentException("object is not a Temperature")
    End Function

    Public Overloads Function ToString(ByVal format As String, ByVal provider As IFormatProvider) As String _
        Implements IFormattable.ToString

        If Not (format Is Nothing) Then
            If format.Equals("F") Then
                Return [String].Format("{0}'F", Me.Value.ToString())
            End If
            If format.Equals("C") Then
                Return [String].Format("{0}'C", Me.Celsius.ToString())
            End If
        End If

        Return m_value.ToString(format, provider)
    End Function

    ' Parses the temperature from a string in form
    ' [ws][sign]digits['F|'C][ws]
    Public Shared Function Parse(ByVal s As String, ByVal styles As NumberStyles, ByVal provider As IFormatProvider) As Temperature
        Dim temp As New Temperature()

        If s.TrimEnd(Nothing).EndsWith("'F") Then
            temp.Value = Double.Parse(s.Remove(s.LastIndexOf("'"c), 2), styles, provider)
        Else
            If s.TrimEnd(Nothing).EndsWith("'C") Then
                temp.Celsius = Double.Parse(s.Remove(s.LastIndexOf("'"c), 2), styles, provider)
            Else
                temp.Value = Double.Parse(s, styles, provider)
            End If
        End If
        Return temp
    End Function

    ' The value holder
    Protected m_value As Double

    Public Property Value() As Double
        Get
            Return m_value
        End Get
        Set(ByVal Value As Double)
            m_value = Value
        End Set
    End Property

    Public Property Celsius() As Double
        Get
            Return (m_value - 32) / 1.8
        End Get
        Set(ByVal Value As Double)
            m_value = Value * 1.8 + 32
        End Set
    End Property
End Class

備註

Double 值型別代表雙精確度64位數位,其值範圍從負面的 1.79769313486232 e 308 到正 1.79769313486232 e 308,以及正數或負零、 PositiveInfinityNegativeInfinity ,而不是數位 (NaN) 。The Double value type represents a double-precision 64-bit number with values ranging from negative 1.79769313486232e308 to positive 1.79769313486232e308, as well as positive or negative zero, PositiveInfinity, NegativeInfinity, and not a number (NaN). 它的目的是要代表極大的 (例如,行星或 galaxies) 之間的距離,或非常小的 ((例如,以) 公斤表示的物質分子品質),這通常是不精確的 (,例如從地球到另一個日光系統) 的距離。It is intended to represent values that are extremely large (such as distances between planets or galaxies) or extremely small (such as the molecular mass of a substance in kilograms) and that often are imprecise (such as the distance from earth to another solar system). Double 類型符合 IEC 60559:1989 (IEEE 754) 標準適用于二進位浮點算術。The Double type complies with the IEC 60559:1989 (IEEE 754) standard for binary floating-point arithmetic.

本主題包含下列章節:This topic consists of the following sections:

Floating-Point 標記法和精確度Floating-Point Representation and Precision

Double資料類型會以64位的二進位格式儲存雙精確度浮點值,如下表所示:The Double data type stores double-precision floating-point values in a 64-bit binary format, as shown in the following table:

部分Part BitsBits
有效位數或尾數Significand or mantissa 0-510-51
指數Exponent 52-6252-62
正負號 (0 = 正數,1 = 負數) Sign (0 = Positive, 1 = Negative) 6363

就像小數部分無法精確呈現某些小數值 (例如1/3 或 Math.PI) ,二進位片段無法表示某些小數值。Just as decimal fractions are unable to precisely represent some fractional values (such as 1/3 or Math.PI), binary fractions are unable to represent some fractional values. 例如,1/10 (由 .1 以小數部分精確表示)以二進位小數001100110011表示,並將 "0011" 模式重複為無限大。For example, 1/10, which is represented precisely by .1 as a decimal fraction, is represented by .001100110011 as a binary fraction, with the pattern "0011" repeating to infinity. 在此情況下,浮點值會提供其所代表之數位的不精確標記法。In this case, the floating-point value provides an imprecise representation of the number that it represents. 對原始浮點值執行其他數學運算通常會增加其缺少的精確度。Performing additional mathematical operations on the original floating-point value often tends to increase its lack of precision. 例如,如果我們比較將 .1 乘以10的結果,並將0.1 加入 1 9 次,我們會發現加法,因為它牽涉到八個以上的作業,所以產生的結果比較不精確。For example, if we compare the result of multiplying .1 by 10 and adding .1 to .1 nine times, we see that addition, because it has involved eight more operations, has produced the less precise result. 請注意,只有當我們 Double 使用 "R" 標準數值格式字串來顯示這兩個值時,才會顯示此差異,如果需要,則會顯示類型所支援的所有17個有效位數 DoubleNote that this disparity is apparent only if we display the two Double values by using the "R" standard numeric format string, which if necessary displays all 17 digits of precision supported by the Double type.

using System;

public class Example
{
   public static void Main()
   {
      Double value = .1;
      Double result1 = value * 10;
      Double result2 = 0;
      for (int ctr = 1; ctr <= 10; ctr++)
         result2 += value;

      Console.WriteLine(".1 * 10:           {0:R}", result1);
      Console.WriteLine(".1 Added 10 times: {0:R}", result2);
   }
}
// The example displays the following output:
//       .1 * 10:           1
//       .1 Added 10 times: 0.99999999999999989
Module Example
   Public Sub Main()
      Dim value As Double = .1
      Dim result1 As Double = value * 10
      Dim result2 As Double
      For ctr As Integer = 1 To 10
         result2 += value
      Next
      Console.WriteLine(".1 * 10:           {0:R}", result1)
      Console.WriteLine(".1 Added 10 times: {0:R}", result2)
   End Sub
End Module
' The example displays the following output:
'       .1 * 10:           1
'       .1 Added 10 times: 0.99999999999999989

因為某些數位無法完全表示為小數二進位值,所以浮點數只能有近似的實數。Because some numbers cannot be represented exactly as fractional binary values, floating-point numbers can only approximate real numbers.

所有浮點數的有效位數也有限制,這也會決定浮點值近似實數的精確程度。All floating-point numbers also have a limited number of significant digits, which also determines how accurately a floating-point value approximates a real number. Double值最多可有15個小數位數,但在內部維護最多17位數。A Double value has up to 15 decimal digits of precision, although a maximum of 17 digits is maintained internally. 這表示某些浮點運算可能缺乏變更浮點值的精確度。This means that some floating-point operations may lack the precision to change a floating point value. 下列範例提供說明。The following example provides an illustration. 它會定義非常大的浮點值,然後在其中加入 Double.Epsilon 和一個 quadrillion 的乘積。It defines a very large floating-point value, and then adds the product of Double.Epsilon and one quadrillion to it. 但是,這項產品太小,無法修改原始的浮點值。The product, however, is too small to modify the original floating-point value. 其最小有效位數為千位數,而產品中最有效的數位為 10-309Its least significant digit is thousandths, whereas the most significant digit in the product is 10-309.

using System;

public class Example
{
   public static void Main()
   {
      Double value = 123456789012.34567;
      Double additional = Double.Epsilon * 1e15;
      Console.WriteLine("{0} + {1} = {2}", value, additional,
                                           value + additional);
   }
}
// The example displays the following output:
//    123456789012.346 + 4.94065645841247E-309 = 123456789012.346
Module Example
   Public Sub Main()
      Dim value As Double = 123456789012.34567
      Dim additional As Double = Double.Epsilon * 1e15
      Console.WriteLine("{0} + {1} = {2}", value, additional, 
                                           value + additional)
   End Sub
End Module
' The example displays the following output:
'   123456789012.346 + 4.94065645841247E-309 = 123456789012.346

浮點數的有限有效位數有數個結果:The limited precision of a floating-point number has several consequences:

  • 對特定有效位數相等的兩個浮點數,可能因為它們的最低有效位數不同,而不相等。Two floating-point numbers that appear equal for a particular precision might not compare equal because their least significant digits are different. 在下列範例中,會將一系列的數位相加,並將其總計與預期的總計進行比較。In the following example, a series of numbers are added together, and their total is compared with their expected total. 雖然這兩個值看似相同,但呼叫 Equals 方法卻表示它們不是。Although the two values appear to be the same, a call to the Equals method indicates that they are not.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double[] values = { 10.0, 2.88, 2.88, 2.88, 9.0 };
          Double result = 27.64;
          Double total = 0;
          foreach (var value in values)
             total += value;
    
          if (total.Equals(result))
             Console.WriteLine("The sum of the values equals the total.");
          else
             Console.WriteLine("The sum of the values ({0}) does not equal the total ({1}).",
                               total, result);
       }
    }
    // The example displays the following output:
    //      The sum of the values (36.64) does not equal the total (36.64).
    //
    // If the index items in the Console.WriteLine statement are changed to {0:R},
    // the example displays the following output:
    //       The sum of the values (27.639999999999997) does not equal the total (27.64).
    
    Module Example
       Public Sub Main()
          Dim values() As Double = { 10.0, 2.88, 2.88, 2.88, 9.0 }
          Dim result As Double = 27.64
          Dim total As Double
          For Each value In values
             total += value
          Next
          If total.Equals(result) Then
             Console.WriteLine("The sum of the values equals the total.")
          Else
             Console.WriteLine("The sum of the values ({0}) does not equal the total ({1}).",
                               total, result) 
          End If     
       End Sub
    End Module
    ' The example displays the following output:
    '      The sum of the values (36.64) does not equal the total (36.64).   
    '
    ' If the index items in the Console.WriteLine statement are changed to {0:R},
    ' the example displays the following output:
    '       The sum of the values (27.639999999999997) does not equal the total (27.64).   
    

    如果您將語句中的格式專案 Console.WriteLine(String, Object, Object){0} 和變更 {1}{0:R} ,並 {1:R} 顯示這兩個值的所有有效位數 Double ,則表示這兩個值不相等,因為在加法運算期間遺失精確度。If you change the format items in the Console.WriteLine(String, Object, Object) statement from {0} and {1} to {0:R} and {1:R} to display all significant digits of the two Double values, it is clear that the two values are unequal because of a loss of precision during the addition operations. 在此情況下,您可以呼叫方法來解決此問題, Math.Round(Double, Int32) 以便在 Double 執行比較之前將值舍入至所需的精確度。In this case, the issue can be resolved by calling the Math.Round(Double, Int32) method to round the Double values to the desired precision before performing the comparison.

  • 如果使用的是十進位數,則使用浮點數的數學或比較運算可能不會產生相同的結果,因為二進位浮點數可能不等於十進位數。A mathematical or comparison operation that uses a floating-point number might not yield the same result if a decimal number is used, because the binary floating-point number might not equal the decimal number. 先前的範例會顯示將 .1 乘以10的結果,並加上. 1 次。A previous example illustrated this by displaying the result of multiplying .1 by 10 and adding .1 times.

    當數值運算中具有小數值的精確度很重要時,您可以使用 Decimal 而不是 Double 類型。When accuracy in numeric operations with fractional values is important, you can use the Decimal rather than the Double type. 如果數值運算中的整數值超出或類型範圍的精確度 Int64 UInt64 很重要,請使用型別 BigIntegerWhen accuracy in numeric operations with integral values beyond the range of the Int64 or UInt64 types is important, use the BigInteger type.

  • 如果涉及浮點數,值可能不會往返。A value might not round-trip if a floating-point number is involved. 如果作業將原始浮點數轉換成另一個表單,反向運算會將轉換後的表單轉換回浮點數,而最後一個浮點數不等於原始浮點數,則會將值視為往返。A value is said to round-trip if an operation converts an original floating-point number to another form, an inverse operation transforms the converted form back to a floating-point number, and the final floating-point number is not equal to the original floating-point number. 來回行程可能會失敗,因為轉換中有一或多個最小的有效位數遺失或變更。The round trip might fail because one or more least significant digits are lost or changed in a conversion. 在下列範例中, Double 會將三個值轉換成字串,並儲存在檔案中。In the following example, three Double values are converted to strings and saved in a file. 不過,輸出會顯示,即使值看似相同,還原的值也不會等於原始值。As the output shows, however, even though the values appear to be identical, the restored values are not equal to the original values.

    using System;
    using System.IO;
    
    public class Example
    {
       public static void Main()
       {
          StreamWriter sw = new StreamWriter(@".\Doubles.dat");
          Double[] values = { 2.2/1.01, 1.0/3, Math.PI };
          for (int ctr = 0; ctr < values.Length; ctr++) {
             sw.Write(values[ctr].ToString());
             if (ctr != values.Length - 1)
                sw.Write("|");
          }
          sw.Close();
    
          Double[] restoredValues = new Double[values.Length];
          StreamReader sr = new StreamReader(@".\Doubles.dat");
          string temp = sr.ReadToEnd();
          string[] tempStrings = temp.Split('|');
          for (int ctr = 0; ctr < tempStrings.Length; ctr++)
             restoredValues[ctr] = Double.Parse(tempStrings[ctr]);
    
          for (int ctr = 0; ctr < values.Length; ctr++)
             Console.WriteLine("{0} {2} {1}", values[ctr],
                               restoredValues[ctr],
                               values[ctr].Equals(restoredValues[ctr]) ? "=" : "<>");
       }
    }
    // The example displays the following output:
    //       2.17821782178218 <> 2.17821782178218
    //       0.333333333333333 <> 0.333333333333333
    //       3.14159265358979 <> 3.14159265358979
    
    Imports System.IO
    
    Module Example
       Public Sub Main()
          Dim sw As New StreamWriter(".\Doubles.dat")
          Dim values() As Double = { 2.2/1.01, 1.0/3, Math.PI }
          For ctr As Integer = 0 To values.Length - 1
             sw.Write(values(ctr).ToString())
             If ctr <> values.Length - 1 Then sw.Write("|")
          Next      
          sw.Close()
          
          Dim restoredValues(values.Length - 1) As Double
          Dim sr As New StreamReader(".\Doubles.dat")
          Dim temp As String = sr.ReadToEnd()
          Dim tempStrings() As String = temp.Split("|"c)
          For ctr As Integer = 0 To tempStrings.Length - 1
             restoredValues(ctr) = Double.Parse(tempStrings(ctr))   
          Next 
    
          For ctr As Integer = 0 To values.Length - 1
             Console.WriteLine("{0} {2} {1}", values(ctr), 
                               restoredValues(ctr),
                               If(values(ctr).Equals(restoredValues(ctr)), "=", "<>"))
          Next
       End Sub
    End Module
    ' The example displays the following output:
    '       2.17821782178218 <> 2.17821782178218
    '       0.333333333333333 <> 0.333333333333333
    '       3.14159265358979 <> 3.14159265358979
    

    在此情況下,可以使用 "G17" 標準數值格式字串 來保留值的完整精確度,以成功地進行往返 Double ,如下列範例所示。In this case, the values can be successfully round-tripped by using the "G17" standard numeric format string to preserve the full precision of Double values, as the following example shows.

    using System;
    using System.IO;
    
    public class Example
    {
       public static void Main()
       {
          StreamWriter sw = new StreamWriter(@".\Doubles.dat");
          Double[] values = { 2.2/1.01, 1.0/3, Math.PI };
          for (int ctr = 0; ctr < values.Length; ctr++)
             sw.Write("{0:G17}{1}", values[ctr], ctr < values.Length - 1 ? "|" : "" );
    
          sw.Close();
    
          Double[] restoredValues = new Double[values.Length];
          StreamReader sr = new StreamReader(@".\Doubles.dat");
          string temp = sr.ReadToEnd();
          string[] tempStrings = temp.Split('|');
          for (int ctr = 0; ctr < tempStrings.Length; ctr++)
             restoredValues[ctr] = Double.Parse(tempStrings[ctr]);
    
          for (int ctr = 0; ctr < values.Length; ctr++)
             Console.WriteLine("{0} {2} {1}", values[ctr],
                               restoredValues[ctr],
                               values[ctr].Equals(restoredValues[ctr]) ? "=" : "<>");
       }
    }
    // The example displays the following output:
    //       2.17821782178218 = 2.17821782178218
    //       0.333333333333333 = 0.333333333333333
    //       3.14159265358979 = 3.14159265358979
    
    Imports System.IO
    
    Module Example
       Public Sub Main()
          Dim sw As New StreamWriter(".\Doubles.dat")
          Dim values() As Double = { 2.2/1.01, 1.0/3, Math.PI }
          For ctr As Integer = 0 To values.Length - 1
             sw.Write("{0:G17}{1}", values(ctr), 
                      If(ctr < values.Length - 1, "|", ""))
          Next      
          sw.Close()
          
          Dim restoredValues(values.Length - 1) As Double
          Dim sr As New StreamReader(".\Doubles.dat")
          Dim temp As String = sr.ReadToEnd()
          Dim tempStrings() As String = temp.Split("|"c)
          For ctr As Integer = 0 To tempStrings.Length - 1
             restoredValues(ctr) = Double.Parse(tempStrings(ctr))   
          Next 
    
          For ctr As Integer = 0 To values.Length - 1
             Console.WriteLine("{0} {2} {1}", values(ctr), 
                               restoredValues(ctr),
                               If(values(ctr).Equals(restoredValues(ctr)), "=", "<>"))
          Next
       End Sub
    End Module
    ' The example displays the following output:
    '       2.17821782178218 = 2.17821782178218
    '       0.333333333333333 = 0.333333333333333
    '       3.14159265358979 = 3.14159265358979
    

重要

搭配值使用時 Double ,在某些情況下,"R" 格式規範無法成功地往返原始值。When used with a Double value, the "R" format specifier in some cases fails to successfully round-trip the original value. 若要確保 Double 值能成功地往返,請使用 "G17" 格式規範。To ensure that Double values successfully round-trip, use the "G17" format specifier.

  • Single 值的精確度低於 Double 值。Single values have less precision than Double values. Single轉換成看似相等的值 Double 通常不會 Double 因為精確度差異而不等於值。A Single value that is converted to a seemingly equivalent Double often does not equal the Double value because of differences in precision. 在下列範例中,會將相同除法作業的結果指派給 DoubleSingle 值。In the following example, the result of identical division operations is assigned to a Double and a Single value. Single當值轉換成之後 Double ,這兩個值的比較會顯示它們不相等。After the Single value is cast to a Double, a comparison of the two values shows that they are unequal.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value1 = 1/3.0;
          Single sValue2 = 1/3.0f;
          Double value2 = (Double) sValue2;
          Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2,
                                              value1.Equals(value2));
       }
    }
    // The example displays the following output:
    //        0.33333333333333331 = 0.3333333432674408: False
    
    Module Example
       Public Sub Main()
          Dim value1 As Double = 1/3
          Dim sValue2 As Single = 1/3
          Dim value2 As Double = CDbl(sValue2)
          Console.WriteLine("{0} = {1}: {2}", value1, value2, value1.Equals(value2))
       End Sub
    End Module
    ' The example displays the following output:
    '       0.33333333333333331 = 0.3333333432674408: False
    

    若要避免這個問題,請使用來 Double 取代 Single 資料類型,或使用 Round 方法讓這兩個值都有相同的精確度。To avoid this problem, use either the Double in place of the Single data type, or use the Round method so that both values have the same precision.

此外,具有值的算術和指派運算結果 Double 可能會因平臺而稍有不同,因為該類型的有效位數遺失 DoubleIn addition, the result of arithmetic and assignment operations with Double values may differ slightly by platform because of the loss of precision of the Double type. 例如,在 Double .NET Framework 的32位和64位版本中,指派常值的結果可能會不同。For example, the result of assigning a literal Double value may differ in the 32-bit and 64-bit versions of the .NET Framework. 下列範例說明當常值 4.42330604244772 E-305 和值為-4.42330604244772 E-305 的變數指派給變數時,這項差異 DoubleThe following example illustrates this difference when the literal value -4.42330604244772E-305 and a variable whose value is -4.42330604244772E-305 are assigned to a Double variable. 請注意, Parse(String) 在此案例中,方法的結果並不會因為精確度遺失而受到影響。Note that the result of the Parse(String) method in this case does not suffer from a loss of precision.

double value = -4.42330604244772E-305;

double fromLiteral = -4.42330604244772E-305;
double fromVariable = value;
double fromParse = Double.Parse("-4.42330604244772E-305");

Console.WriteLine("Double value from literal: {0,29:R}", fromLiteral);
Console.WriteLine("Double value from variable: {0,28:R}", fromVariable);
Console.WriteLine("Double value from Parse method: {0,24:R}", fromParse);
// On 32-bit versions of the .NET Framework, the output is:
//    Double value from literal:        -4.42330604244772E-305
//    Double value from variable:       -4.42330604244772E-305
//    Double value from Parse method:   -4.42330604244772E-305
//
// On other versions of the .NET Framework, the output is:
//    Double value from literal:      -4.4233060424477198E-305
//    Double value from variable:     -4.4233060424477198E-305
//    Double value from Parse method:   -4.42330604244772E-305
Dim value As Double = -4.42330604244772E-305

Dim fromLiteral As Double = -4.42330604244772E-305
Dim fromVariable As Double = value
Dim fromParse As Double = Double.Parse("-4.42330604244772E-305")

Console.WriteLine("Double value from literal: {0,29:R}", fromLiteral)
Console.WriteLine("Double value from variable: {0,28:R}", fromVariable)
Console.WriteLine("Double value from Parse method: {0,24:R}", fromParse)      
' On 32-bit versions of the .NET Framework, the output is:
'    Double value from literal:        -4.42330604244772E-305
'    Double value from variable:       -4.42330604244772E-305
'    Double value from Parse method:   -4.42330604244772E-305
'
' On other versions of the .NET Framework, the output is:
'    Double value from literal:        -4.4233060424477198E-305
'    Double value from variable:       -4.4233060424477198E-305
'    Double value from Parse method:     -4.42330604244772E-305      

測試是否相等Testing for Equality

若要視為相等,兩個 Double 值必須代表相同的值。To be considered equal, two Double values must represent identical values. 不過,由於值之間的精確度有差異,或由於一或兩個值的精確度遺失,所以預期會相同的浮點值通常會因為其最少的數位差異而變成不相等。However, because of differences in precision between values, or because of a loss of precision by one or both values, floating-point values that are expected to be identical often turn out to be unequal because of differences in their least significant digits. 因此,呼叫 Equals 方法來判斷兩個值是否相等,或呼叫 CompareTo 方法來判斷兩個值之間的關聯性 Double ,通常會產生非預期的結果。As a result, calls to the Equals method to determine whether two values are equal, or calls to the CompareTo method to determine the relationship between two Double values, often yield unexpected results. 這在下列範例中很明顯,其中兩個明顯相等的 Double 值會變成不相等,因為第一個具有15位數的精確度,而第二個有17個位數。This is evident in the following example, where two apparently equal Double values turn out to be unequal because the first has 15 digits of precision, while the second has 17.

using System;

public class Example
{
   public static void Main()
   {
      double value1 = .333333333333333;
      double value2 = 1.0/3;
      Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2));
   }
}
// The example displays the following output:
//        0.333333333333333 = 0.33333333333333331: False
Module Example
   Public Sub Main()
      Dim value1 As Double = .333333333333333
      Dim value2 As Double = 1/3
      Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2))
   End Sub
End Module
' The example displays the following output:
'       0.333333333333333 = 0.33333333333333331: False

在不同的程式碼路徑之後,以不同的方式操作的計算值通常會證明不相等。Calculated values that follow different code paths and that are manipulated in different ways often prove to be unequal. 在下列範例中,有一個 Double 值是平方,然後計算平方根來還原原始值。In the following example, one Double value is squared, and then the square root is calculated to restore the original value. 第二個 Double 會乘以3.51 和平方,而結果的平方根會除以3.51 以還原原始值。A second Double is multiplied by 3.51 and squared before the square root of the result is divided by 3.51 to restore the original value. 雖然這兩個值看似相同,但呼叫 Equals(Double) 方法表示它們不相等。Although the two values appear to be identical, a call to the Equals(Double) method indicates that they are not equal. 使用 "R" 標準格式字串來傳回結果字串,以顯示每個雙精度浮點數的所有有效位數,表示第二個值的 .0000000000001 小於第一個值。Using the "R" standard format string to return a result string that displays all the significant digits of each Double value shows that the second value is .0000000000001 less than the first.

using System;

public class Example
{
   public static void Main()
   {
      double value1 = 100.10142;
      value1 = Math.Sqrt(Math.Pow(value1, 2));
      double value2 = Math.Pow(value1 * 3.51, 2);
      value2 = Math.Sqrt(value2) / 3.51;
      Console.WriteLine("{0} = {1}: {2}\n",
                        value1, value2, value1.Equals(value2));
      Console.WriteLine("{0:R} = {1:R}", value1, value2);
   }
}
// The example displays the following output:
//    100.10142 = 100.10142: False
//
//    100.10142 = 100.10141999999999
Module Example
   Public Sub Main()
      Dim value1 As Double = 100.10142
      value1 = Math.Sqrt(Math.Pow(value1, 2))
      Dim value2 As Double = Math.Pow(value1 * 3.51, 2)
      value2 = Math.Sqrt(value2) / 3.51
      Console.WriteLine("{0} = {1}: {2}", 
                        value1, value2, value1.Equals(value2)) 
      Console.WriteLine()
      Console.WriteLine("{0:R} = {1:R}", value1, value2) 
   End Sub
End Module
' The example displays the following output:
'    100.10142 = 100.10142: False
'    
'    100.10142 = 100.10141999999999

如果遺失有效位數的情況可能會影響比較的結果,您可以採用下列任何一種方法來呼叫 EqualsCompareTo 方法:In cases where a loss of precision is likely to affect the result of a comparison, you can adopt any of the following alternatives to calling the Equals or CompareTo method:

  • 呼叫 Math.Round 方法,以確定兩個值都有相同的有效位數。Call the Math.Round method to ensure that both values have the same precision. 下列範例會修改先前的範例,以使用這種方法,使兩個小數值相等。The following example modifies a previous example to use this approach so that two fractional values are equivalent.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          double value1 = .333333333333333;
          double value2 = 1.0/3;
          int precision = 7;
          value1 = Math.Round(value1, precision);
          value2 = Math.Round(value2, precision);
          Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2));
       }
    }
    // The example displays the following output:
    //        0.3333333 = 0.3333333: True
    
    Module Example
       Public Sub Main()
          Dim value1 As Double = .333333333333333
          Dim value2 As Double = 1/3
          Dim precision As Integer = 7
          value1 = Math.Round(value1, precision)
          value2 = Math.Round(value2, precision)
          Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2))
       End Sub
    End Module
    ' The example displays the following output:
    '       0.3333333 = 0.3333333: True
    

    不過要注意的是,精確度的問題仍然適用于將中間點值四捨五入。Note, though, that the problem of precision still applies to rounding of midpoint values. 如需詳細資訊,請參閱 Math.Round(Double, Int32, MidpointRounding) 方法。For more information, see the Math.Round(Double, Int32, MidpointRounding) method.

  • 測試大約相等,而不是相等。Test for approximate equality rather than equality. 這需要您定義兩個值可以不同但仍相等的絕對數量,或您定義較小值可與較大值分離的相對數量。This requires that you define either an absolute amount by which the two values can differ but still be equal, or that you define a relative amount by which the smaller value can diverge from the larger value.

    警告

    Double.Epsilon 測試是否相等時,有時會用來做為兩個值之間的距離的絕對量值 DoubleDouble.Epsilon is sometimes used as an absolute measure of the distance between two Double values when testing for equality. 但是, Double.Epsilon 測量的最小可能值為零,可新增至或從中減去的值 DoubleHowever, Double.Epsilon measures the smallest possible value that can be added to, or subtracted from, a Double whose value is zero. 對於大部分的正值和負值 Double ,的值 Double.Epsilon 太小而無法偵測到。For most positive and negative Double values, the value of Double.Epsilon is too small to be detected. 因此,除了零以外的值,我們不建議在測試中使用相等的值。Therefore, except for values that are zero, we do not recommend its use in tests for equality.

    下列範例會使用第二種方法來定義 IsApproximatelyEqual 方法,以測試兩個值之間的相對差異。The following example uses the latter approach to define an IsApproximatelyEqual method that tests the relative difference between two values. 此外,它也會比較呼叫 IsApproximatelyEqual 方法和方法的結果 Equals(Double)It also contrasts the result of calls to the IsApproximatelyEqual method and the Equals(Double) method.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          double one1 = .1 * 10;
          double one2 = 0;
          for (int ctr = 1; ctr <= 10; ctr++)
             one2 += .1;
    
          Console.WriteLine("{0:R} = {1:R}: {2}", one1, one2, one1.Equals(one2));
          Console.WriteLine("{0:R} is approximately equal to {1:R}: {2}",
                            one1, one2,
                            IsApproximatelyEqual(one1, one2, .000000001));
       }
    
       static bool IsApproximatelyEqual(double value1, double value2, double epsilon)
       {
          // If they are equal anyway, just return True.
          if (value1.Equals(value2))
             return true;
    
          // Handle NaN, Infinity.
          if (Double.IsInfinity(value1) | Double.IsNaN(value1))
             return value1.Equals(value2);
          else if (Double.IsInfinity(value2) | Double.IsNaN(value2))
             return value1.Equals(value2);
    
          // Handle zero to avoid division by zero
          double divisor = Math.Max(value1, value2);
          if (divisor.Equals(0))
             divisor = Math.Min(value1, value2);
    
          return Math.Abs((value1 - value2) / divisor) <= epsilon;
       }
    }
    // The example displays the following output:
    //       1 = 0.99999999999999989: False
    //       1 is approximately equal to 0.99999999999999989: True
    
    Module Example
       Public Sub Main()
          Dim one1 As Double = .1 * 10
          Dim one2 As Double = 0
          For ctr As Integer = 1 To 10
             one2 += .1
          Next
          Console.WriteLine("{0:R} = {1:R}: {2}", one1, one2, one1.Equals(one2))
          Console.WriteLine("{0:R} is approximately equal to {1:R}: {2}", 
                            one1, one2, 
                            IsApproximatelyEqual(one1, one2, .000000001))   
       End Sub
    
       Function IsApproximatelyEqual(value1 As Double, value2 As Double, 
                                     epsilon As Double) As Boolean
          ' If they are equal anyway, just return True.
          If value1.Equals(value2) Then Return True
          
          ' Handle NaN, Infinity.
          If Double.IsInfinity(value1) Or Double.IsNaN(value1) Then
             Return value1.Equals(value2)
          Else If Double.IsInfinity(value2) Or Double.IsNaN(value2)
             Return value1.Equals(value2)
          End If
          
          ' Handle zero to avoid division by zero
          Dim divisor As Double = Math.Max(value1, value2)
          If divisor.Equals(0) Then
             divisor = Math.Min(value1, value2)
          End If 
          
          Return Math.Abs((value1 - value2) / divisor) <= epsilon           
       End Function
    End Module
    ' The example displays the following output:
    '       1 = 0.99999999999999989: False
    '       1 is approximately equal to 0.99999999999999989: True
    

Floating-Point 的值和例外狀況Floating-Point Values and Exceptions

不同于具有整數類資料類型的作業,這會在溢位或不合法作業(例如零除)時擲回例外狀況,但具有浮點值的作業不會擲回例外狀況。Unlike operations with integral types, which throw exceptions in cases of overflow or illegal operations such as division by zero, operations with floating-point values do not throw exceptions. 相反地,在例外狀況下,浮點運算的結果為零、正無限大、負無限大或不是數位 (NaN) :Instead, in exceptional situations, the result of a floating-point operation is zero, positive infinity, negative infinity, or not a number (NaN):

  • 如果浮點運算的結果對目的格式而言太小,則結果為零。If the result of a floating-point operation is too small for the destination format, the result is zero. 當兩個非常小的數位相乘時,就會發生這種情況,如下列範例所示。This can occur when two very small numbers are multiplied, as the following example shows.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value1 = 1.1632875981534209e-225;
          Double value2 = 9.1642346778e-175;
          Double result = value1 * value2;
          Console.WriteLine("{0} * {1} = {2}", value1, value2, result);
          Console.WriteLine("{0} = 0: {1}", result, result.Equals(0.0));
       }
    }
    // The example displays the following output:
    //       1.16328759815342E-225 * 9.1642346778E-175 = 0
    //       0 = 0: True
    
    Module Example
       Public Sub Main()
          Dim value1 As Double = 1.1632875981534209e-225
          Dim value2 As Double = 9.1642346778e-175
          Dim result As Double = value1 * value2
          Console.WriteLine("{0} * {1} = {2}", value1, value2, result)
          Console.WriteLine("{0} = 0: {1}", result, result.Equals(0.0))
       End Sub
    End Module
    ' The example displays the following output:
    '       1.16328759815342E-225 * 9.1642346778E-175 = 0
    '       0 = 0: True
    
  • 如果浮點運算的結果量超過目的格式的範圍,則作業的結果會是 PositiveInfinityNegativeInfinity ,適用于結果的正負號。If the magnitude of the result of a floating-point operation exceeds the range of the destination format, the result of the operation is PositiveInfinity or NegativeInfinity, as appropriate for the sign of the result. 溢位的作業結果為 Double.MaxValue ,而溢位的作業結果為 PositiveInfinity Double.MinValue NegativeInfinity ,如下列範例所示。The result of an operation that overflows Double.MaxValue is PositiveInfinity, and the result of an operation that overflows Double.MinValue is NegativeInfinity, as the following example shows.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value1 = 4.565e153;
          Double value2 = 6.9375e172;
          Double result = value1 * value2;
          Console.WriteLine("PositiveInfinity: {0}",
                             Double.IsPositiveInfinity(result));
          Console.WriteLine("NegativeInfinity: {0}\n",
                            Double.IsNegativeInfinity(result));
    
          value1 = -value1;
          result = value1 * value2;
          Console.WriteLine("PositiveInfinity: {0}",
                             Double.IsPositiveInfinity(result));
          Console.WriteLine("NegativeInfinity: {0}",
                            Double.IsNegativeInfinity(result));
       }
    }
    
    // The example displays the following output:
    //       PositiveInfinity: True
    //       NegativeInfinity: False
    //
    //       PositiveInfinity: False
    //       NegativeInfinity: True
    
    Module Example
       Public Sub Main()
          Dim value1 As Double = 4.565e153
          Dim value2 As Double = 6.9375e172
          Dim result As Double = value1 * value2
          Console.WriteLine("PositiveInfinity: {0}", 
                             Double.IsPositiveInfinity(result))
          Console.WriteLine("NegativeInfinity: {0}", 
                            Double.IsNegativeInfinity(result))
          Console.WriteLine()                  
          value1 = -value1
          result = value1 * value2
          Console.WriteLine("PositiveInfinity: {0}", 
                             Double.IsPositiveInfinity(result))
          Console.WriteLine("NegativeInfinity: {0}", 
                            Double.IsNegativeInfinity(result))
       End Sub
    End Module
    ' The example displays the following output:
    '       PositiveInfinity: True
    '       NegativeInfinity: False
    '       
    '       PositiveInfinity: False
    '       NegativeInfinity: True
    

    PositiveInfinity 另外也會產生除數為零的結果,並以 NegativeInfinity 負被除數的零除結果。PositiveInfinity also results from a division by zero with a positive dividend, and NegativeInfinity results from a division by zero with a negative dividend.

  • 如果浮點運算無效,運算的結果就是 NaNIf a floating-point operation is invalid, the result of the operation is NaN. 例如, NaN 下列作業的結果:For example, NaN results from the following operations:

  • 具有無效輸入的任何浮點運算。Any floating-point operation with an invalid input. 例如, Math.Sqrt 使用負數值來呼叫方法 NaN 會傳回,就像 Math.Acos 使用大於一或小於負一的值來呼叫方法一樣。For example, calling the Math.Sqrt method with a negative value returns NaN, as does calling the Math.Acos method with a value that is greater than one or less than negative one.

  • 具有值為之引數的任何作業 Double.NaNAny operation with an argument whose value is Double.NaN.

類型轉換和雙重結構Type conversions and the Double structure

Double結構不會定義任何明確或隱含的轉換運算子; 相反地,轉換是由編譯器所執行。The Double structure does not define any explicit or implicit conversion operators; instead, conversions are implemented by the compiler.

將任何基本數數值型別的值轉換為 Double 擴輾轉換,因此不需要明確的轉換運算子或對轉換方法的呼叫,除非編譯器明確需要它。The conversion of the value of any primitive numeric type to a Double is a widening conversion and therefore does not require an explicit cast operator or call to a conversion method unless a compiler explicitly requires it. 例如,c # 編譯器需要轉換運算子 Decimal ,才能從轉換成 Double ,Visual Basic 編譯器則不需要。For example, the C# compiler requires a casting operator for conversions from Decimal to Double, while the Visual Basic compiler does not. 下列範例會將其他基本數數值型別的最小值或最大值轉換成 DoubleThe following example converts the minimum or maximum value of other primitive numeric types to a Double.

using System;

public class Example
{
   public static void Main()
   {
      dynamic[] values = { Byte.MinValue, Byte.MaxValue, Decimal.MinValue,
                           Decimal.MaxValue, Int16.MinValue, Int16.MaxValue,
                           Int32.MinValue, Int32.MaxValue, Int64.MinValue,
                           Int64.MaxValue, SByte.MinValue, SByte.MaxValue,
                           Single.MinValue, Single.MaxValue, UInt16.MinValue,
                           UInt16.MaxValue, UInt32.MinValue, UInt32.MaxValue,
                           UInt64.MinValue, UInt64.MaxValue };
      double dblValue;
      foreach (var value in values) {
         if (value.GetType() == typeof(Decimal))
            dblValue = (Double) value;
         else
            dblValue = value;
         Console.WriteLine("{0} ({1}) --> {2:R} ({3})",
                           value, value.GetType().Name,
                           dblValue, dblValue.GetType().Name);
      }
   }
}
// The example displays the following output:
//    0 (Byte) --> 0 (Double)
//    255 (Byte) --> 255 (Double)
//    -79228162514264337593543950335 (Decimal) --> -7.9228162514264338E+28 (Double)
//    79228162514264337593543950335 (Decimal) --> 7.9228162514264338E+28 (Double)
//    -32768 (Int16) --> -32768 (Double)
//    32767 (Int16) --> 32767 (Double)
//    -2147483648 (Int32) --> -2147483648 (Double)
//    2147483647 (Int32) --> 2147483647 (Double)
//    -9223372036854775808 (Int64) --> -9.2233720368547758E+18 (Double)
//    9223372036854775807 (Int64) --> 9.2233720368547758E+18 (Double)
//    -128 (SByte) --> -128 (Double)
//    127 (SByte) --> 127 (Double)
//    -3.402823E+38 (Single) --> -3.4028234663852886E+38 (Double)
//    3.402823E+38 (Single) --> 3.4028234663852886E+38 (Double)
//    0 (UInt16) --> 0 (Double)
//    65535 (UInt16) --> 65535 (Double)
//    0 (UInt32) --> 0 (Double)
//    4294967295 (UInt32) --> 4294967295 (Double)
//    0 (UInt64) --> 0 (Double)
//    18446744073709551615 (UInt64) --> 1.8446744073709552E+19 (Double)
Module Example
   Public Sub Main()
      Dim values() As Object = { Byte.MinValue, Byte.MaxValue, Decimal.MinValue,
                                 Decimal.MaxValue, Int16.MinValue, Int16.MaxValue,
                                 Int32.MinValue, Int32.MaxValue, Int64.MinValue,
                                 Int64.MaxValue, SByte.MinValue, SByte.MaxValue,
                                 Single.MinValue, Single.MaxValue, UInt16.MinValue,
                                 UInt16.MaxValue, UInt32.MinValue, UInt32.MaxValue,
                                 UInt64.MinValue, UInt64.MaxValue }
      Dim dblValue As Double
      For Each value In values
         dblValue = value
         Console.WriteLine("{0} ({1}) --> {2:R} ({3})",
                           value, value.GetType().Name,
                           dblValue, dblValue.GetType().Name)
      Next
   End Sub
End Module
' The example displays the following output:
'    0 (Byte) --> 0 (Double)
'    255 (Byte) --> 255 (Double)
'    -79228162514264337593543950335 (Decimal) --> -7.9228162514264338E+28 (Double)
'    79228162514264337593543950335 (Decimal) --> 7.9228162514264338E+28 (Double)
'    -32768 (Int16) --> -32768 (Double)
'    32767 (Int16) --> 32767 (Double)
'    -2147483648 (Int32) --> -2147483648 (Double)
'    2147483647 (Int32) --> 2147483647 (Double)
'    -9223372036854775808 (Int64) --> -9.2233720368547758E+18 (Double)
'    9223372036854775807 (Int64) --> 9.2233720368547758E+18 (Double)
'    -128 (SByte) --> -128 (Double)
'    127 (SByte) --> 127 (Double)
'    -3.402823E+38 (Single) --> -3.4028234663852886E+38 (Double)
'    3.402823E+38 (Single) --> 3.4028234663852886E+38 (Double)
'    0 (UInt16) --> 0 (Double)
'    65535 (UInt16) --> 65535 (Double)
'    0 (UInt32) --> 0 (Double)
'    4294967295 (UInt32) --> 4294967295 (Double)
'    0 (UInt64) --> 0 (Double)
'    18446744073709551615 (UInt64) --> 1.8446744073709552E+19 (Double)

此外, SingleSingle.NaN 、和會 Single.PositiveInfinity Single.NegativeInfinity 分別轉換為 Double.NaN 、和 Double.PositiveInfinity Double.NegativeInfinityIn addition, the Single values Single.NaN, Single.PositiveInfinity, and Single.NegativeInfinity convert to Double.NaN, Double.PositiveInfinity, and Double.NegativeInfinity, respectively.

請注意,將某些數數值型別的值轉換成值時, Double 可能會遺失有效位數。Note that the conversion of the value of some numeric types to a Double value can involve a loss of precision. 如範例所示,將 DecimalInt64Single 和值轉換成 UInt64 Double 值時,可能會失去精確度。As the example illustrates, a loss of precision is possible when converting Decimal, Int64, Single, and UInt64 values to Double values.

Double 值轉換成任何其他基本數值資料類型的值是縮小轉換,而且需要在 c # ) 中 (轉換運算子、Visual Basic) 中 (的轉換方法,或對方法的呼叫 ConvertThe conversion of a Double value to a value of any other primitive numeric data type is a narrowing conversion and requires a cast operator (in C#), a conversion method (in Visual Basic), or a call to a Convert method. 目標資料類型範圍以外的值(由目標型別和屬性定義)的 MinValue MaxValue 行為如下表所示。Values that are outside the range of the target data type, which are defined by the target type's MinValue and MaxValue properties, behave as shown in the following table.

目標類型Target type 結果Result
任何整數類型Any integral type OverflowException如果是在已檢查的內容中進行轉換,則為例外狀況。An OverflowException exception if the conversion occurs in a checked context.

如果在未檢查的內容中進行轉換 (c # ) 中的預設值,則轉換作業會成功,但值會溢位。If the conversion occurs in an unchecked context (the default in C#), the conversion operation succeeds but the value overflows.
Decimal OverflowException 例外狀況。An OverflowException exception.
Single Single.NegativeInfinity 適用于負數值。Single.NegativeInfinity for negative values.

Single.PositiveInfinity 適用于正值。Single.PositiveInfinity for positive values.

此外,在 Double.NaN 檢查的內容中,、和會擲回以 Double.PositiveInfinity Double.NegativeInfinity OverflowException 轉換成整數,但在未檢查的內容中轉換成整數時,這些值會溢位。In addition, Double.NaN, Double.PositiveInfinity, and Double.NegativeInfinity throw an OverflowException for conversions to integers in a checked context, but these values overflow when converted to integers in an unchecked context. 針對的轉換 Decimal ,它們一律會擲回 OverflowExceptionFor conversions to Decimal, they always throw an OverflowException. 針對的轉換 Single ,它們會分別轉換為 Single.NaNSingle.PositiveInfinitySingle.NegativeInfinityFor conversions to Single, they convert to Single.NaN, Single.PositiveInfinity, and Single.NegativeInfinity, respectively.

請注意,遺失有效位數可能是因為將 Double 值轉換成另一個數數值型別。Note that a loss of precision may result from converting a Double value to another numeric type. 在轉換非整數值的情況下, Double 如範例的輸出所示,當 Double 值是四捨五入 (如 Visual Basic) 或截斷 ((如同在 c # ) 中)時,就會遺失小陣列件。In the case of converting non-integral Double values, as the output from the example shows, the fractional component is lost when the Double value is either rounded (as in Visual Basic) or truncated (as in C#). 若為 Decimal 和值的轉換 SingleDouble 值可能不會在目標資料類型中有精確的表示。For conversions to Decimal and Single values, the Double value may not have a precise representation in the target data type.

下列範例會將數個 Double 值轉換成其他數個數數值型別。The following example converts a number of Double values to several other numeric types. 轉換會在 Visual Basic 的已檢查內容中進行, (預設) 和 c # (,因為 checked 關鍵字) 。The conversions occur in a checked context in Visual Basic (the default) and in C# (because of the checked keyword). 範例的輸出會顯示已檢查的未檢查內容中,轉換的結果。The output from the example shows the result for conversions in both a checked an unchecked context. 您可以使用編譯器參數進行編譯 /removeintchecks+ ,並在 c # 中將語句標記為批註,以在 Visual Basic 的未檢查內容中執行轉換 checkedYou can perform conversions in an unchecked context in Visual Basic by compiling with the /removeintchecks+ compiler switch and in C# by commenting out the checked statement.

using System;

public class Example
{
   public static void Main()
   {
      Double[] values = { Double.MinValue, -67890.1234, -12345.6789,
                          12345.6789, 67890.1234, Double.MaxValue,
                          Double.NaN, Double.PositiveInfinity,
                          Double.NegativeInfinity };
      checked {
         foreach (var value in values) {
            try {
                Int64 lValue = (long) value;
                Console.WriteLine("{0} ({1}) --> {2} (0x{2:X16}) ({3})",
                                  value, value.GetType().Name,
                                  lValue, lValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to Int64.", value);
            }
            try {
                UInt64 ulValue = (ulong) value;
                Console.WriteLine("{0} ({1}) --> {2} (0x{2:X16}) ({3})",
                                  value, value.GetType().Name,
                                  ulValue, ulValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to UInt64.", value);
            }
            try {
                Decimal dValue = (decimal) value;
                Console.WriteLine("{0} ({1}) --> {2} ({3})",
                                  value, value.GetType().Name,
                                  dValue, dValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to Decimal.", value);
            }
            try {
                Single sValue = (float) value;
                Console.WriteLine("{0} ({1}) --> {2} ({3})",
                                  value, value.GetType().Name,
                                  sValue, sValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to Single.", value);
            }
            Console.WriteLine();
         }
      }
   }
}
// The example displays the following output for conversions performed
// in a checked context:
//       Unable to convert -1.79769313486232E+308 to Int64.
//       Unable to convert -1.79769313486232E+308 to UInt64.
//       Unable to convert -1.79769313486232E+308 to Decimal.
//       -1.79769313486232E+308 (Double) --> -Infinity (Single)
//
//       -67890.1234 (Double) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
//       Unable to convert -67890.1234 to UInt64.
//       -67890.1234 (Double) --> -67890.1234 (Decimal)
//       -67890.1234 (Double) --> -67890.13 (Single)
//
//       -12345.6789 (Double) --> -12345 (0xFFFFFFFFFFFFCFC7) (Int64)
//       Unable to convert -12345.6789 to UInt64.
//       -12345.6789 (Double) --> -12345.6789 (Decimal)
//       -12345.6789 (Double) --> -12345.68 (Single)
//
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (Int64)
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (UInt64)
//       12345.6789 (Double) --> 12345.6789 (Decimal)
//       12345.6789 (Double) --> 12345.68 (Single)
//
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (Int64)
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (UInt64)
//       67890.1234 (Double) --> 67890.1234 (Decimal)
//       67890.1234 (Double) --> 67890.13 (Single)
//
//       Unable to convert 1.79769313486232E+308 to Int64.
//       Unable to convert 1.79769313486232E+308 to UInt64.
//       Unable to convert 1.79769313486232E+308 to Decimal.
//       1.79769313486232E+308 (Double) --> Infinity (Single)
//
//       Unable to convert NaN to Int64.
//       Unable to convert NaN to UInt64.
//       Unable to convert NaN to Decimal.
//       NaN (Double) --> NaN (Single)
//
//       Unable to convert Infinity to Int64.
//       Unable to convert Infinity to UInt64.
//       Unable to convert Infinity to Decimal.
//       Infinity (Double) --> Infinity (Single)
//
//       Unable to convert -Infinity to Int64.
//       Unable to convert -Infinity to UInt64.
//       Unable to convert -Infinity to Decimal.
//       -Infinity (Double) --> -Infinity (Single)
// The example displays the following output for conversions performed
// in an unchecked context:
//       -1.79769313486232E+308 (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       -1.79769313486232E+308 (Double) --> 9223372036854775808 (0x8000000000000000) (UInt64)
//       Unable to convert -1.79769313486232E+308 to Decimal.
//       -1.79769313486232E+308 (Double) --> -Infinity (Single)
//
//       -67890.1234 (Double) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
//       -67890.1234 (Double) --> 18446744073709483726 (0xFFFFFFFFFFFEF6CE) (UInt64)
//       -67890.1234 (Double) --> -67890.1234 (Decimal)
//       -67890.1234 (Double) --> -67890.13 (Single)
//
//       -12345.6789 (Double) --> -12345 (0xFFFFFFFFFFFFCFC7) (Int64)
//       -12345.6789 (Double) --> 18446744073709539271 (0xFFFFFFFFFFFFCFC7) (UInt64)
//       -12345.6789 (Double) --> -12345.6789 (Decimal)
//       -12345.6789 (Double) --> -12345.68 (Single)
//
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (Int64)
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (UInt64)
//       12345.6789 (Double) --> 12345.6789 (Decimal)
//       12345.6789 (Double) --> 12345.68 (Single)
//
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (Int64)
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (UInt64)
//       67890.1234 (Double) --> 67890.1234 (Decimal)
//       67890.1234 (Double) --> 67890.13 (Single)
//
//       1.79769313486232E+308 (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       1.79769313486232E+308 (Double) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert 1.79769313486232E+308 to Decimal.
//       1.79769313486232E+308 (Double) --> Infinity (Single)
//
//       NaN (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       NaN (Double) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert NaN to Decimal.
//       NaN (Double) --> NaN (Single)
//
//       Infinity (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       Infinity (Double) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert Infinity to Decimal.
//       Infinity (Double) --> Infinity (Single)
//
//       -Infinity (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       -Infinity (Double) --> 9223372036854775808 (0x8000000000000000) (UInt64)
//       Unable to convert -Infinity to Decimal.
//       -Infinity (Double) --> -Infinity (Single)
Module Example
   Public Sub Main()
      Dim values() As Double = { Double.MinValue, -67890.1234, -12345.6789,
                                 12345.6789, 67890.1234, Double.MaxValue,
                                 Double.NaN, Double.PositiveInfinity,
                                 Double.NegativeInfinity }
      For Each value In values
         Try
             Dim lValue As Int64 = CLng(value)
             Console.WriteLine("{0} ({1}) --> {2} (0x{2:X16}) ({3})",
                               value, value.GetType().Name,
                               lValue, lValue.GetType().Name)
         Catch e As OverflowException
            Console.WriteLine("Unable to convert {0} to Int64.", value)
         End Try
         Try
             Dim ulValue As UInt64 = CULng(value)
             Console.WriteLine("{0} ({1}) --> {2} (0x{2:X16}) ({3})",
                               value, value.GetType().Name,
                               ulValue, ulValue.GetType().Name)
         Catch e As OverflowException
            Console.WriteLine("Unable to convert {0} to UInt64.", value)
         End Try
         Try
             Dim dValue As Decimal = CDec(value)
             Console.WriteLine("{0} ({1}) --> {2} ({3})",
                               value, value.GetType().Name,
                               dValue, dValue.GetType().Name)
         Catch e As OverflowException
            Console.WriteLine("Unable to convert {0} to Decimal.", value)
         End Try
         Try
             Dim sValue As Single = CSng(value)
             Console.WriteLine("{0} ({1}) --> {2} ({3})",
                               value, value.GetType().Name,
                               sValue, sValue.GetType().Name)
         Catch e As OverflowException
            Console.WriteLine("Unable to convert {0} to Single.", value)
         End Try
         Console.WriteLine()
      Next
   End Sub
End Module
' The example displays the following output for conversions performed
' in a checked context:
'       Unable to convert -1.79769313486232E+308 to Int64.
'       Unable to convert -1.79769313486232E+308 to UInt64.
'       Unable to convert -1.79769313486232E+308 to Decimal.
'       -1.79769313486232E+308 (Double) --> -Infinity (Single)
'
'       -67890.1234 (Double) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
'       Unable to convert -67890.1234 to UInt64.
'       -67890.1234 (Double) --> -67890.1234 (Decimal)
'       -67890.1234 (Double) --> -67890.13 (Single)
'
'       -12345.6789 (Double) --> -12346 (0xFFFFFFFFFFFFCFC6) (Int64)
'       Unable to convert -12345.6789 to UInt64.
'       -12345.6789 (Double) --> -12345.6789 (Decimal)
'       -12345.6789 (Double) --> -12345.68 (Single)
'
'       12345.6789 (Double) --> 12346 (0x000000000000303A) (Int64)
'       12345.6789 (Double) --> 12346 (0x000000000000303A) (UInt64)
'       12345.6789 (Double) --> 12345.6789 (Decimal)
'       12345.6789 (Double) --> 12345.68 (Single)
'
'       67890.1234 (Double) --> 67890 (0x0000000000010932) (Int64)
'       67890.1234 (Double) --> 67890 (0x0000000000010932) (UInt64)
'       67890.1234 (Double) --> 67890.1234 (Decimal)
'       67890.1234 (Double) --> 67890.13 (Single)
'
'       Unable to convert 1.79769313486232E+308 to Int64.
'       Unable to convert 1.79769313486232E+308 to UInt64.
'       Unable to convert 1.79769313486232E+308 to Decimal.
'       1.79769313486232E+308 (Double) --> Infinity (Single)
'
'       Unable to convert NaN to Int64.
'       Unable to convert NaN to UInt64.
'       Unable to convert NaN to Decimal.
'       NaN (Double) --> NaN (Single)
'
'       Unable to convert Infinity to Int64.
'       Unable to convert Infinity to UInt64.
'       Unable to convert Infinity to Decimal.
'       Infinity (Double) --> Infinity (Single)
'
'       Unable to convert -Infinity to Int64.
'       Unable to convert -Infinity to UInt64.
'       Unable to convert -Infinity to Decimal.
'       -Infinity (Double) --> -Infinity (Single)
' The example displays the following output for conversions performed
' in an unchecked context:
'       -1.79769313486232E+308 (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       -1.79769313486232E+308 (Double) --> 9223372036854775808 (0x8000000000000000) (UInt64)
'       Unable to convert -1.79769313486232E+308 to Decimal.
'       -1.79769313486232E+308 (Double) --> -Infinity (Single)
'
'       -67890.1234 (Double) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
'       -67890.1234 (Double) --> 18446744073709483726 (0xFFFFFFFFFFFEF6CE) (UInt64)
'       -67890.1234 (Double) --> -67890.1234 (Decimal)
'       -67890.1234 (Double) --> -67890.13 (Single)
'
'       -12345.6789 (Double) --> -12346 (0xFFFFFFFFFFFFCFC6) (Int64)
'       -12345.6789 (Double) --> 18446744073709539270 (0xFFFFFFFFFFFFCFC6) (UInt64)
'       -12345.6789 (Double) --> -12345.6789 (Decimal)
'       -12345.6789 (Double) --> -12345.68 (Single)
'
'       12345.6789 (Double) --> 12346 (0x000000000000303A) (Int64)
'       12345.6789 (Double) --> 12346 (0x000000000000303A) (UInt64)
'       12345.6789 (Double) --> 12345.6789 (Decimal)
'       12345.6789 (Double) --> 12345.68 (Single)
'
'       67890.1234 (Double) --> 67890 (0x0000000000010932) (Int64)
'       67890.1234 (Double) --> 67890 (0x0000000000010932) (UInt64)
'       67890.1234 (Double) --> 67890.1234 (Decimal)
'       67890.1234 (Double) --> 67890.13 (Single)
'
'       1.79769313486232E+308 (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       1.79769313486232E+308 (Double) --> 0 (0x0000000000000000) (UInt64)
'       Unable to convert 1.79769313486232E+308 to Decimal.
'       1.79769313486232E+308 (Double) --> Infinity (Single)
'
'       NaN (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       NaN (Double) --> 0 (0x0000000000000000) (UInt64)
'       Unable to convert NaN to Decimal.
'       NaN (Double) --> NaN (Single)
'
'       Infinity (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       Infinity (Double) --> 0 (0x0000000000000000) (UInt64)
'       Unable to convert Infinity to Decimal.
'       Infinity (Double) --> Infinity (Single)
'
'       -Infinity (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       -Infinity (Double) --> 9223372036854775808 (0x8000000000000000) (UInt64)
'       Unable to convert -Infinity to Decimal.
'       -Infinity (Double) --> -Infinity (Single)

如需數數值型別轉換的詳細資訊,請參閱 .NET Framework類型轉換表中的型別轉換。For more information on the conversion of numeric types, see Type Conversion in the .NET Framework and Type Conversion Tables.

Floating-Point 功能Floating-Point Functionality

Double結構和相關類型提供在下欄區域中執行作業的方法:The Double structure and related types provide methods to perform operations in the following areas:

  • 值的比較Comparison of values. 您可以呼叫 Equals 方法來判斷兩個 Double 值是否相等,或 CompareTo 方法來判斷兩個值之間的關聯性。You can call the Equals method to determine whether two Double values are equal, or the CompareTo method to determine the relationship between two values.

    Double 結構也支援一組完整的比較運算子。The Double structure also supports a complete set of comparison operators. 例如,您可以測試是否相等或不相等,或判斷某個值是否大於或等於另一個值。For example, you can test for equality or inequality, or determine whether one value is greater than or equal to another. 如果其中一個運算元是以外的數數值型別,則會 Double 先將它轉換成, Double 再執行比較。If one of the operands is a numeric type other than a Double, it is converted to a Double before performing the comparison.

    警告

    因為精確度差異, Double 您預期相等的兩個值可能會變得不相等,而這會影響比較的結果。Because of differences in precision, two Double values that you expect to be equal may turn out to be unequal, which affects the result of the comparison. 如需比較兩個值的詳細資訊,請參閱 測試是否相等 一節 DoubleSee the Testing for Equality section for more information about comparing two Double values.

    您也可以呼叫 IsNaNIsInfinityIsPositiveInfinityIsNegativeInfinity 方法來測試這些特殊值。You can also call the IsNaN, IsInfinity, IsPositiveInfinity, and IsNegativeInfinity methods to test for these special values.

  • 數學運算Mathematical operations. 常見的算數運算(例如加法、減法、乘法和除法)是由語言編譯器和通用中繼語言 (CIL) 指令,而不是透過方法來執行 DoubleCommon arithmetic operations, such as addition, subtraction, multiplication, and division, are implemented by language compilers and Common Intermediate Language (CIL) instructions, rather than by Double methods. 如果數學運算中的其中一個運算元是 a 以外的數數值型別,則會 Double 先將它轉換成, Double 再執行作業。If one of the operands in a mathematical operation is a numeric type other than a Double, it is converted to a Double before performing the operation. 運算的結果也是 Double 值。The result of the operation is also a Double value.

    您可以藉由呼叫 static Shared 類別中 Visual Basic) 方法的 (來執行其他數學運算 System.MathOther mathematical operations can be performed by calling static (Shared in Visual Basic) methods in the System.Math class. 它包含通常用於算術 (的其他方法,例如 Math.Abs 、和 Math.Sign Math.Sqrt) 、幾何 (例如 Math.CosMath.Sin) ,以及微積分 (,例如 Math.Log) 。It includes additional methods commonly used for arithmetic (such as Math.Abs, Math.Sign, and Math.Sqrt), geometry (such as Math.Cos and Math.Sin), and calculus (such as Math.Log).

    您也可以操控值中的個別位 DoubleYou can also manipulate the individual bits in a Double value. BitConverter.DoubleToInt64Bits方法會 Double 在64位整數中保留值的位模式。The BitConverter.DoubleToInt64Bits method preserves a Double value's bit pattern in a 64-bit integer. BitConverter.GetBytes(Double)方法會在位元組陣列中傳回其位模式。The BitConverter.GetBytes(Double) method returns its bit pattern in a byte array.

  • 四捨五入Rounding. 舍入通常用來做為減少浮點表示和精確度問題所造成之值的影響的技術。Rounding is often used as a technique for reducing the impact of differences between values caused by problems of floating-point representation and precision. 您可以藉 Double 由呼叫方法來舍入值 Math.RoundYou can round a Double value by calling the Math.Round method.

  • 格式化Formatting. 您可以藉 Double 由呼叫 ToString 方法或使用複合格式功能,將值轉換成其字串表示。You can convert a Double value to its string representation by calling the ToString method or by using the composite formatting feature. 如需格式字串如何控制浮點值之字串表示的詳細資訊,請參閱 標準數值格式字串自訂數值格式字串 主題。For information about how format strings control the string representation of floating-point values, see the Standard Numeric Format Strings and Custom Numeric Format Strings topics.

  • 剖析字串Parsing strings. 您可以藉 Double 由呼叫或方法,將浮點值的字串表示轉換為值 Parse TryParseYou can convert the string representation of a floating-point value to a Double value by calling either the Parse or TryParse method. 如果剖析作業失敗,則方法會擲回 Parse 例外狀況,而方法則會傳回 TryParse falseIf the parse operation fails, the Parse method throws an exception, whereas the TryParse method returns false.

  • 類型轉換Type conversion. Double結構會提供介面的明確介面實 IConvertible ,以支援任何兩個標準 .NET Framework 資料類型之間的轉換。The Double structure provides an explicit interface implementation for the IConvertible interface, which supports conversion between any two standard .NET Framework data types. 語言編譯器也支援將所有其他標準數數值型別的值隱含轉換成 Double 值。Language compilers also support the implicit conversion of values of all other standard numeric types to Double values. 任何標準數數值型別的值轉換為 Double 擴輾轉換,而且不需要轉換運算子或轉換方法的使用者,Conversion of a value of any standard numeric type to a Double is a widening conversion and does not require the user of a casting operator or conversion method,

    但是, Int64 和值的轉換 Single 可能會遺失有效位數。However, conversion of Int64 and Single values can involve a loss of precision. 下表列出每一種類型的精確度差異:The following table lists the differences in precision for each of these types:

    類型Type 最大有效位數Maximum precision 內部精確度Internal precision
    Double 1515 1717
    Int64 19個小數位數19 decimal digits 19個小數位數19 decimal digits
    Single 7個小數位數7 decimal digits 9個小數位數9 decimal digits

    精確度最頻繁的問題會影響 Single 轉換成值的值 DoubleThe problem of precision most frequently affects Single values that are converted to Double values. 在下列範例中,相同除法運算所產生的兩個值不相等,因為其中一個值是轉換成的單精確度浮點值 DoubleIn the following example, two values produced by identical division operations are unequal because one of the values is a single-precision floating point value converted to a Double.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value = .1;
          Double result1 = value * 10;
          Double result2 = 0;
          for (int ctr = 1; ctr <= 10; ctr++)
             result2 += value;
    
          Console.WriteLine(".1 * 10:           {0:R}", result1);
          Console.WriteLine(".1 Added 10 times: {0:R}", result2);
       }
    }
    // The example displays the following output:
    //       .1 * 10:           1
    //       .1 Added 10 times: 0.99999999999999989
    
    Module Example
       Public Sub Main()
          Dim value As Double = .1
          Dim result1 As Double = value * 10
          Dim result2 As Double
          For ctr As Integer = 1 To 10
             result2 += value
          Next
          Console.WriteLine(".1 * 10:           {0:R}", result1)
          Console.WriteLine(".1 Added 10 times: {0:R}", result2)
       End Sub
    End Module
    ' The example displays the following output:
    '       .1 * 10:           1
    '       .1 Added 10 times: 0.99999999999999989
    

欄位

Epsilon

代表大於零的最小正 Double 值。Represents the smallest positive Double value that is greater than zero. 這個欄位為常數。This field is constant.

MaxValue

表示 Double 最大的可能值。Represents the largest possible value of a Double. 這個欄位為常數。This field is constant.

MinValue

表示 Double 最小的可能值。Represents the smallest possible value of a Double. 這個欄位為常數。This field is constant.

NaN

代表不是數字 (NaN) 的值。Represents a value that is not a number (NaN). 這個欄位為常數。This field is constant.

NegativeInfinity

表示負無限大。Represents negative infinity. 這個欄位為常數。This field is constant.

PositiveInfinity

表示正無限大。Represents positive infinity. 這個欄位為常數。This field is constant.

方法

CompareTo(Double)

比較這個執行個體與雙精確度的浮點數值,並且傳回一個整數,指出這個執行個體的值是小於、等於或大於特定的雙精確度浮點數值。Compares this instance to a specified double-precision floating-point number and returns an integer that indicates whether the value of this instance is less than, equal to, or greater than the value of the specified double-precision floating-point number.

CompareTo(Object)

比較這個執行個體與特定物件,並且傳回一個整數,指出這個執行個體的值是小於、等於或大於特定物件的值。Compares this instance to a specified object and returns an integer that indicates whether the value of this instance is less than, equal to, or greater than the value of the specified object.

Equals(Double)

傳回值,該值表示這個執行個體和指定的 Double 物件是否代表相同值。Returns a value indicating whether this instance and a specified Double object represent the same value.

Equals(Object)

傳回值,該值表示這個執行個體是否和指定的物件相等。Returns a value indicating whether this instance is equal to a specified object.

GetHashCode()

傳回這個執行個體的雜湊碼。Returns the hash code for this instance.

GetTypeCode()

傳回實值類型 TypeCodeDoubleReturns the TypeCode for value type Double.

IsFinite(Double)

判斷指定的值是否為有限 (零、偏低或一般)。Determines whether the specified value is finite (zero, subnormal, or normal).

IsInfinity(Double)

傳回值,指出指定的數字是否計算結果為負或正的無限大。Returns a value indicating whether the specified number evaluates to negative or positive infinity.

IsNaN(Double)

傳回值,該值表示指定的值是否不是數字 (NaN)。Returns a value that indicates whether the specified value is not a number (NaN).

IsNegative(Double)

判斷指定的值是否為負數。Determines whether the specified value is negative.

IsNegativeInfinity(Double)

傳回值,指出指定的數字是否計算結果為負的無限大。Returns a value indicating whether the specified number evaluates to negative infinity.

IsNormal(Double)

判斷指定的值是否為正常。Determines whether the specified value is normal.

IsPositiveInfinity(Double)

傳回值,指出指定數字是否計算結果為正的無限大。Returns a value indicating whether the specified number evaluates to positive infinity.

IsSubnormal(Double)

判斷指定的值是否為偏低。Determines whether the specified value is subnormal.

Parse(ReadOnlySpan<Char>, NumberStyles, IFormatProvider)

將包含數字字串表示 (使用指定樣式和特定文化特性格式) 的字元範圍轉換為其對等的雙精確度浮點數。Converts a character span that contains the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent.

Parse(String)

將數字的字串表示轉換為其相等的雙精確度浮點數。Converts the string representation of a number to its double-precision floating-point number equivalent.

Parse(String, IFormatProvider)

將數字的字串表示 (使用指定的特定文化特性格式) 轉換為其相等的雙精確度浮點數。Converts the string representation of a number in a specified culture-specific format to its double-precision floating-point number equivalent.

Parse(String, NumberStyles)

將數字的字串表示 (使用指定樣式) 轉換為其相等的雙精確度浮點數。Converts the string representation of a number in a specified style to its double-precision floating-point number equivalent.

Parse(String, NumberStyles, IFormatProvider)

使用指定樣式和特定文化特性格式,將數字的字串表示轉換為其相等的雙精確度浮點數。Converts the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent.

ToString()

將這個執行個體的數值轉換為其相等字串表示。Converts the numeric value of this instance to its equivalent string representation.

ToString(IFormatProvider)

使用指定的特定文化特性格式資訊,將這個執行個體的數值轉換成它的相等字串表示。Converts the numeric value of this instance to its equivalent string representation using the specified culture-specific format information.

ToString(String)

使用指定格式,將這個執行個體的數值轉換成它的相等字串表示。Converts the numeric value of this instance to its equivalent string representation, using the specified format.

ToString(String, IFormatProvider)

使用指定的格式和特定文化特性格式資訊,將這個執行個體的數值轉換成它的相等字串表示。Converts the numeric value of this instance to its equivalent string representation using the specified format and culture-specific format information.

TryFormat(Span<Char>, Int32, ReadOnlySpan<Char>, IFormatProvider)

嘗試將目前雙精確度浮點數執行個體的值格式化為所提供的字元範圍。Tries to format the value of the current double instance into the provided span of characters.

TryParse(ReadOnlySpan<Char>, Double)

將數字的範圍表示 (使用指定樣式和特定文化特性格式) 轉換為其對等的雙精確度浮點數。Converts the span representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent. 傳回值,該值指出轉換成功或失敗。A return value indicates whether the conversion succeeded or failed.

TryParse(ReadOnlySpan<Char>, NumberStyles, IFormatProvider, Double)

將包含數字字串表示 (使用指定樣式和特定文化特性格式) 的字元範圍轉換為其對等的雙精確度浮點數。Converts a character span containing the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent. 傳回值,該值指出轉換成功或失敗。A return value indicates whether the conversion succeeded or failed.

TryParse(String, Double)

將數字的字串表示轉換為其相等的雙精確度浮點數。Converts the string representation of a number to its double-precision floating-point number equivalent. 傳回值,該值指出轉換成功或失敗。A return value indicates whether the conversion succeeded or failed.

TryParse(String, NumberStyles, IFormatProvider, Double)

使用指定樣式和特定文化特性格式,將數字的字串表示轉換為其相等的雙精確度浮點數。Converts the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent. 傳回值,該值指出轉換成功或失敗。A return value indicates whether the conversion succeeded or failed.

運算子

Equality(Double, Double)

傳回值,該值表示兩個指定的 Double 值是否相等。Returns a value that indicates whether two specified Double values are equal.

GreaterThan(Double, Double)

傳回值,該值表示指定的 Double 值是否大於另一個指定的 Double 值。Returns a value that indicates whether a specified Double value is greater than another specified Double value.

GreaterThanOrEqual(Double, Double)

傳回值,該值表示指定的 Double 值是否大於或等於另一個指定的 Double 值。Returns a value that indicates whether a specified Double value is greater than or equal to another specified Double value.

Inequality(Double, Double)

傳回值,該值表示兩個指定的 Double 值是否不相等。Returns a value that indicates whether two specified Double values are not equal.

LessThan(Double, Double)

傳回值,該值表示指定的 Double 值是否小於另一個指定的 Double 值。Returns a value that indicates whether a specified Double value is less than another specified Double value.

LessThanOrEqual(Double, Double)

傳回值,該值表示指定的 Double 值是否小於或等於另一個指定的 Double 值。Returns a value that indicates whether a specified Double value is less than or equal to another specified Double value.

明確介面實作

IComparable.CompareTo(Object)

將目前的執行個體與相同類型的另一個物件相比較,並傳回整數,這個整數表示目前的執行個體在排序次序中,位於另一個物件之前、之後或相同位置。Compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

IConvertible.GetTypeCode()

傳回這個執行個體的 TypeCodeReturns the TypeCode for this instance.

IConvertible.ToBoolean(IFormatProvider)

如需這個成員的說明,請參閱 ToBoolean(IFormatProvider)For a description of this member, see ToBoolean(IFormatProvider).

IConvertible.ToByte(IFormatProvider)

如需這個成員的說明,請參閱 ToByte(IFormatProvider)For a description of this member, see ToByte(IFormatProvider).

IConvertible.ToChar(IFormatProvider)

不支援此轉換。This conversion is not supported. 嘗試使用這個方法會擲回 InvalidCastExceptionAttempting to use this method throws an InvalidCastException.

IConvertible.ToDateTime(IFormatProvider)

不支援此轉換。This conversion is not supported. 嘗試使用這個方法會擲回 InvalidCastExceptionAttempting to use this method throws an InvalidCastException

IConvertible.ToDecimal(IFormatProvider)

如需這個成員的說明,請參閱 ToDecimal(IFormatProvider)For a description of this member, see ToDecimal(IFormatProvider).

IConvertible.ToDouble(IFormatProvider)

如需這個成員的說明,請參閱 ToDouble(IFormatProvider)For a description of this member, see ToDouble(IFormatProvider).

IConvertible.ToInt16(IFormatProvider)

如需這個成員的說明,請參閱 ToInt16(IFormatProvider)For a description of this member, see ToInt16(IFormatProvider).

IConvertible.ToInt32(IFormatProvider)

如需這個成員的說明,請參閱 ToInt32(IFormatProvider)For a description of this member, see ToInt32(IFormatProvider).

IConvertible.ToInt64(IFormatProvider)

如需這個成員的說明,請參閱 ToInt64(IFormatProvider)For a description of this member, see ToInt64(IFormatProvider).

IConvertible.ToSByte(IFormatProvider)

如需這個成員的說明,請參閱 ToSByte(IFormatProvider)For a description of this member, see ToSByte(IFormatProvider).

IConvertible.ToSingle(IFormatProvider)

如需這個成員的說明,請參閱 ToSingle(IFormatProvider)For a description of this member, see ToSingle(IFormatProvider).

IConvertible.ToType(Type, IFormatProvider)

如需這個成員的說明,請參閱 ToType(Type, IFormatProvider)For a description of this member, see ToType(Type, IFormatProvider).

IConvertible.ToUInt16(IFormatProvider)

如需這個成員的說明,請參閱 ToUInt16(IFormatProvider)For a description of this member, see ToUInt16(IFormatProvider).

IConvertible.ToUInt32(IFormatProvider)

如需這個成員的說明,請參閱 ToUInt32(IFormatProvider)For a description of this member, see ToUInt32(IFormatProvider).

IConvertible.ToUInt64(IFormatProvider)

如需這個成員的說明,請參閱 ToUInt64(IFormatProvider)For a description of this member, see ToUInt64(IFormatProvider).

適用於

執行緒安全性

此類型的所有成員都是安全線程。All members of this type are thread safe. 看似修改實例狀態的成員,實際上會傳回以新值初始化的新實例。Members that appear to modify instance state actually return a new instance initialized with the new value. 如同任何其他類型,讀取和寫入包含此類型之實例的共用變數,都必須受到鎖定的保護,以保證執行緒安全。As with any other type, reading and writing to a shared variable that contains an instance of this type must be protected by a lock to guarantee thread safety.

另請參閱