# SingleSingleSingleSingle Struct

## 定義

``public value class Single : IComparable, IComparable<float>, IConvertible, IEquatable<float>, IFormattable``
``````[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public struct Single : IComparable, IComparable<float>, IConvertible, IEquatable<float>, IFormattable``````
``````type single = struct
interface IFormattable
interface IConvertible``````
``````Public Structure Single
Implements IComparable, IComparable(Of Single), IConvertible, IEquatable(Of Single), IFormattable``````

SingleSingleSingleSingle

## 備註

System.Single提供方法來比較這個類型的實例、將實例的值轉換成其字串表示, 以及將數位的字串表示轉換成這個類型的實例。System.Single provides methods to compare instances of this type, to convert the value of an instance to its string representation, and to convert the string representation of a number to an instance of this type. 如需格式規格代碼如何控制數值型別的字串標記法的詳細資訊, 請參閱格式化類型標準數值格式字串自訂數值格式字串For information about how format specification codes control the string representation of value types, see Formatting Types, Standard Numeric Format Strings, and Custom Numeric Format Strings.

### 浮點表示和有效位數Floating-point representation and precision

Single資料類型會以32位的二進位格式儲存單精確度浮點值, 如下表所示:The Single data type stores single-precision floating-point values in a 32-bit binary format, as shown in the following table:

Exponent 23-3023-30
Sign (0 = 正數, 1 = 負數)Sign (0 = positive, 1 = negative) 3131

``````using System;

public class Example
{
public static void Main()
{
Single value = .2f;
Single result1 = value * 10f;
Single result2 = 0f;
for (int ctr = 1; ctr <= 10; ctr++)
result2 += value;

Console.WriteLine(".2 * 10:           {0:R}", result1);
Console.WriteLine(".2 Added 10 times: {0:R}", result2);
}
}
// The example displays the following output:
//       .2 * 10:           2
//       .2 Added 10 times: 2.00000024
``````
``````Module Example
Public Sub Main()
Dim value As Single = .2
Dim result1 As Single = value * 10
Dim result2 As Single
For ctr As Integer = 1 To 10
result2 += value
Next
Console.WriteLine(".2 * 10:           {0:R}", result1)
Console.WriteLine(".2 Added 10 times: {0:R}", result2)
End Sub
End Module
' The example displays the following output:
'       .2 * 10:           2
'       .2 Added 10 times: 2.00000024
``````

``````using System;

public class Example
{
public static void Main()
{
Single value = 123.456f;
Single additional = Single.Epsilon * 1e15f;
}
}
// The example displays the following output:
//    123.456 + 1.401298E-30 = 123.456
``````
``````Module Example
Public Sub Main()
Dim value As Single = 123.456
Dim additional As Single = Single.Epsilon * 1e15
End Sub
End Module
' The example displays the following output:
'   123.456 + 1.401298E-30 = 123.456
``````

• 針對特定有效位數顯示為相等的兩個浮點數, 可能不會比較相等, 因為它們的最小值不相同。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, 會將一連串的數位相加, 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. 雖然兩個值看起來是相同的, 但呼叫`Equals`方法會指出它們不是。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()
{
Single[] values = { 10.01f, 2.88f, 2.88f, 2.88f, 9.0f };
Single result = 27.65f;
Single total = 0f;
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 (27.65) does not equal the total (27.65).
//
// 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 (27.6500015) does not equal the total (27.65).
``````
``````Module Example
Public Sub Main()
Dim values() As Single = { 10.01, 2.88, 2.88, 2.88, 9.0 }
Dim result As Single = 27.65
Dim total As Single
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 (27.65) does not equal the total (27.65).
'
' 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Console.WriteLine(String, Object, Object)將語句中的格式專案從`{0}``{1}` `{0:R}`變更為和`{1:R}` , 以顯示這兩個Single值的所有有效位數, 則表示這兩個值不相等, 因為在加法運算期間遺失有效位數。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 Single 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Math.Round(Double, Int32)方法來解決此問題, 以便在執行比較之前將Single值舍入為所需的有效位數。In this case, the issue can be resolved by calling the Math.Round(Double, Int32) method to round the Single values to the desired precision before performing the comparison.

• 如果使用十進位數, 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 .3 乘以10並將 .3 加入至 3 9 次的結果, 以說明這一點。A previous example illustrated this by displaying the result of multiplying .3 by 10 and adding .3 to .3 nine times.

當數值運算中具有小數值的精確度很重要時, Decimal請使用類型, Single而不是類型。When accuracy in numeric operations with fractional values is important, use the Decimal type instead of the Single type. 當數值運算中的整數值精確度超過Int64UInt64類型的範圍時, 請使用BigInteger類型。When 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種形式, 則會將值稱為來回行程, 反向運算會將轉換後的表單轉換回浮點數, 而最後一個浮點數等於原始的浮點數字。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 equal to the original floating-point number. 來回行程可能會失敗, 因為轉換中遺失或變更了一或多個最不重要的數位。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, 會Single將三個值轉換成字串, 並儲存在檔案中。In the following example, three Single values are converted to strings and saved in a file. 如輸出所示, 雖然值看似相同, 但還原的值不等於原始值。As the output shows, although 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(@".\Singles.dat");
Single[] values = { 3.2f/1.11f, 1.0f/3f, (float) Math.PI };
for (int ctr = 0; ctr < values.Length; ctr++) {
sw.Write(values[ctr].ToString());
if (ctr != values.Length - 1)
sw.Write("|");
}
sw.Close();

Single[] restoredValues = new Single[values.Length];
string[] tempStrings = temp.Split('|');
for (int ctr = 0; ctr < tempStrings.Length; ctr++)
restoredValues[ctr] = Single.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:
//       2.882883 <> 2.882883
//       0.3333333 <> 0.3333333
//       3.141593 <> 3.141593
``````
``````Imports System.IO

Module Example
Public Sub Main()
Dim sw As New StreamWriter(".\Singles.dat")
Dim values() As Single = { 3.2/1.11, 1.0/3, CSng(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 Single
Dim temp As String = sr.ReadToEnd()
Dim tempStrings() As String = temp.Split("|"c)
For ctr As Integer = 0 To tempStrings.Length - 1
restoredValues(ctr) = Single.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:
'        2.882883 <> 2.882883
'        0.3333333 <> 0.3333333
'        3.141593 <> 3.141593
``````

在此情況下, 您可以使用 "G9"標準數值格式字串來保留Single值的完整精確度, 以成功地進行迴圈, 如下列範例所示。In this case, the values can be successfully round-tripped by using the "G9" standard numeric format string to preserve the full precision of Single values, as the following example shows.

``````using System;
using System.IO;

public class Example
{
public static void Main()
{
StreamWriter sw = new StreamWriter(@".\Singles.dat");
Single[] values = { 3.2f/1.11f, 1.0f/3f, (float) Math.PI };
for (int ctr = 0; ctr < values.Length; ctr++)
sw.Write("{0:G9}{1}", values[ctr], ctr < values.Length - 1 ? "|" : "" );

sw.Close();

Single[] restoredValues = new Single[values.Length];
string[] tempStrings = temp.Split('|');
for (int ctr = 0; ctr < tempStrings.Length; ctr++)
restoredValues[ctr] = Single.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:
//       2.882883 = 2.882883
//       0.3333333 = 0.3333333
//       3.141593 = 3.141593
``````
``````Imports System.IO

Module Example
Public Sub Main()
Dim sw As New StreamWriter(".\Singles.dat")
Dim values() As Single = { 3.2/1.11, 1.0/3, CSng(Math.PI)  }
For ctr As Integer = 0 To values.Length - 1
sw.Write("{0:G9}{1}", values(ctr),
If(ctr < values.Length - 1, "|", ""))
Next
sw.Close()

Dim restoredValues(values.Length - 1) As Single
Dim temp As String = sr.ReadToEnd()
Dim tempStrings() As String = temp.Split("|"c)
For ctr As Integer = 0 To tempStrings.Length - 1
restoredValues(ctr) = Single.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:
'       2.882883 = 2.882883
'       0.3333333 = 0.3333333
'       3.141593 = 3.141593
``````
• Single值的精確度Double小於值。Single values have less precision than Double values. 轉換成看似相等DoubleDouble 值通常不等於值,因為有效位數的差異。SingleA 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, 相同除法運算的結果會指派給DoubleSingle和值。In the following example, the result of identical division operations is assigned to a Double value and a Single value. Single值轉換Double成之後, 這兩個值的比較會顯示兩者不相等。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Double資料類型來取代Single資料Round類型, 或使用方法, 讓這兩個值具有相同的有效位數。To avoid this problem, either use the Double data type in place of the Single data type, or use the Round method so that both values have the same precision.

### 測試是否相等Testing for equality

``````using System;

public class Example
{
public static void Main()
{
float value1 = .3333333f;
float value2 = 1.0f/3;
Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2));
}
}
// The example displays the following output:
//        0.3333333 = 0.333333343: False
``````
``````Module Example
Public Sub Main()
Dim value1 As Single = .3333333
Dim value2 As Single = 1/3
Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2))
End Sub
End Module
' The example displays the following output:
'       0.3333333 = 0.333333343: False
``````

``````using System;

public class Example
{
public static void Main()
{
float value1 = 10.201438f;
value1 = (float) Math.Sqrt((float) Math.Pow(value1, 2));
float value2 = (float) Math.Pow((float) value1 * 3.51f, 2);
value2 = ((float) Math.Sqrt(value2)) / 3.51f;
Console.WriteLine("{0} = {1}: {2}\n",
value1, value2, value1.Equals(value2));
Console.WriteLine("{0:G9} = {1:G9}", value1, value2);
}
}
// The example displays the following output:
//       10.20144 = 10.20144: False
//
//       10.201438 = 10.2014389
``````
``````Module Example
Public Sub Main()
Dim value1 As Single = 10.201438
value1 = CSng(Math.Sqrt(CSng(Math.Pow(value1, 2))))
Dim value2 As Single = CSng(Math.Pow(value1 * CSng(3.51), 2))
value2 = CSng(Math.Sqrt(value2) / CSng(3.51))
Console.WriteLine("{0} = {1}: {2}",
value1, value2, value1.Equals(value2))
Console.WriteLine()
Console.WriteLine("{0:G9} = {1:G9}", value1, value2)
End Sub
End Module
' The example displays the following output:
'       10.20144 = 10.20144: False
'
'       10.201438 = 10.2014389
``````

• Math.Round呼叫方法, 以確保這兩個值具有相同的有效位數。Call the Math.Round method to ensure that both values have the same precision. 下列範例會修改前一個範例, 以使用此方法, 讓兩個小數值相等。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()
{
float value1 = .3333333f;
float value2 = 1.0f/3;
int precision = 7;
value1 = (float) Math.Round(value1, precision);
value2 = (float) 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 Single = .3333333
Dim value2 As Single = 1/3
Dim precision As Integer = 7
value1 = CSng(Math.Round(value1, precision))
value2 = CSng(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
``````

請注意, 精確度的問題仍然適用于中間值的圓角。Note 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.

• 測試近似相等, 而不是相等。Test for approximate equality instead of equality. 這項技術需要您定義一個絕對值, 讓這兩個值可以不同但仍然相等, 或者您定義較小的值可以與較大值分離的相對量。This technique 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

Single.Epsilon在測試是否相等時, 有時會當做兩個Single值之間距離的絕對量值使用。Single.Epsilon is sometimes used as an absolute measure of the distance between two Single values when testing for equality. 不過, Single.Epsilon會測量可以加入或減去Single其值為零的最小可能值。However, Single.Epsilon measures the smallest possible value that can be added to, or subtracted from, a Single whose value is zero. 對於大部分的正值Single和負值, 的Single.Epsilon值太小, 無法偵測到。For most positive and negative Single values, the value of Single.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它來進行相等。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個方法來定義`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. 它也會對比呼叫`IsApproximatelyEqual`方法Equals(Single)和方法的結果。It also contrasts the result of calls to the `IsApproximatelyEqual` method and the Equals(Single) method.

``````using System;

public class Example
{
public static void Main()
{
float one1 = .1f * 10;
float one2 = 0f;
for (int ctr = 1; ctr <= 10; ctr++)
one2 += .1f;

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, .000001f));
}

static bool IsApproximatelyEqual(float value1, float value2, float 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 = 1.00000012: False
//       1 is approximately equal to 1.00000012: True
``````
``````Module Example
Public Sub Main()
Dim one1 As Single = .1 * 10
Dim one2 As Single = 0
For ctr As Integer = 1 To 10
one2 += CSng(.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, .000001))
End Sub

Function IsApproximatelyEqual(value1 As Single, value2 As Single,
epsilon As Single) As Boolean
' If they are equal anyway, just return True.
If value1.Equals(value2) Then Return True

' Handle NaN, Infinity.
If Single.IsInfinity(value1) Or Single.IsNaN(value1) Then
Return value1.Equals(value2)
Else If Single.IsInfinity(value2) Or Single.IsNaN(value2)
Return value1.Equals(value2)
End If

' Handle zero to avoid division by zero
Dim divisor As Single = 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 = 1.00000012: False
'       1 is approximately equal to 1.00000012: True
``````

### 浮點值和例外狀況Floating-point values and exceptions

• 如果浮點運算的結果太小而無法用於目的地格式, 則結果會是零。If the result of a floating-point operation is too small for the destination format, the result is zero. 當兩個非常小的浮點數相乘時, 就會發生這種情況, 如下列範例所示。This can occur when two very small floating-point numbers are multiplied, as the following example shows.

``````using System;

public class Example
{
public static void Main()
{
float value1 = 1.163287e-36f;
float value2 = 9.164234e-25f;
float result = value1 * value2;
Console.WriteLine("{0} * {1} = {2}", value1, value2, result);
Console.WriteLine("{0} = 0: {1}", result, result.Equals(0.0f));
}
}
// The example displays the following output:
//       1.163287E-36 * 9.164234E-25 = 0
//       0 = 0: True
``````
``````Module Example
Public Sub Main()
Dim value1 As Single = 1.163287e-36
Dim value2 As Single = 9.164234e-25
Dim result As Single = value1 * value2
Console.WriteLine("{0} * {1} = {2:R}", value1, value2, result)
Console.WriteLine("{0} = 0: {1}", result, result.Equals(0))
End Sub
End Module
' The example displays the following output:
'       1.163287E-36 * 9.164234E-25 = 0
'       0 = 0: True
``````
• 如果浮點運算的結果大小超過目的地格式的範圍, 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Single.MaxValue結果是PositiveInfinity, 而溢位的運算Single.MinValue結果是NegativeInfinity, 如下列範例所示。The result of an operation that overflows Single.MaxValue is PositiveInfinity, and the result of an operation that overflows Single.MinValue is NegativeInfinity, as the following example shows.

``````using System;

public class Example
{
public static void Main()
{
float value1 = 3.065e35f;
float value2 = 6.9375e32f;
float result = value1 * value2;
Console.WriteLine("PositiveInfinity: {0}",
Single.IsPositiveInfinity(result));
Console.WriteLine("NegativeInfinity: {0}\n",
Single.IsNegativeInfinity(result));

value1 = -value1;
result = value1 * value2;
Console.WriteLine("PositiveInfinity: {0}",
Single.IsPositiveInfinity(result));
Console.WriteLine("NegativeInfinity: {0}",
Single.IsNegativeInfinity(result));
}
}

// The example displays the following output:
//       PositiveInfinity: True
//       NegativeInfinity: False
//
//       PositiveInfinity: False
//       NegativeInfinity: True
``````
``````Module Example
Public Sub Main()
Dim value1 As Single = 3.065e35
Dim value2 As Single = 6.9375e32
Dim result As Single = value1 * value2
Console.WriteLine("PositiveInfinity: {0}",
Single.IsPositiveInfinity(result))
Console.WriteLine("NegativeInfinity: {0}",
Single.IsNegativeInfinity(result))
Console.WriteLine()
value1 = -value1
result = value1 * value2
Console.WriteLine("PositiveInfinity: {0}",
Single.IsPositiveInfinity(result))
Console.WriteLine("NegativeInfinity: {0}",
Single.IsNegativeInfinity(result))
End Sub
End Module
' The example displays the following output:
'       PositiveInfinity: True
'       NegativeInfinity: False
'
'       PositiveInfinity: False
'       NegativeInfinity: True
``````

PositiveInfinity此外, 除數為零和正被除數的結果, 以及NegativeInfinity除數為零的結果除以負的負數。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, 作業的結果會是NaNIf a floating-point operation is invalid, the result of the operation is NaN. 例如, NaN來自下列作業的結果:For example, NaN results from the following operations:

• 零除, 除數為零。Division by zero with a dividend of zero. 請注意, 零除的其他情況會導致PositiveInfinity或。 NegativeInfinityNote that other cases of division by zero result in either PositiveInfinity or NegativeInfinity.

• 任何具有無效輸入的浮點運算。Any floating-point operation with invalid input. 例如, 嘗試尋找負數值NaN的平方根會傳回。For example, attempting to find the square root of a negative value returns NaN.

• 具有值為Single.NaN之引數的任何運算。Any operation with an argument whose value is Single.NaN.

### 型別轉換和單一結構Type conversions and the Single structure

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

Conversion from 擴展/縮小Widening/narrowing 可能遺失精確度Possible loss of precision
Byte WideningWidening No
Decimal WideningWidening

Double 縮小超出範圍的值會轉換成Double.NegativeInfinity或。 Double.PositiveInfinityNarrowing; out-of-range values are converted to Double.NegativeInfinity or Double.PositiveInfinity. 可以。Yes. Double支援17個小數位數, 也就是Single支援9。Double supports 17 decimal digits of precision; Single supports 9.
Int16 WideningWidening No
Int32 WideningWidening 可以。Yes. Int32支援10個十進位數的有效位數;Single支援9。Int32 supports 10 decimal digits of precision; Single supports 9.
Int64 WideningWidening 可以。Yes. Int64支援19個十進位數的有效位數;Single支援9。Int64 supports 19 decimal digits of precision; Single supports 9.
SByte WideningWidening No
UInt16 WideningWidening No
UInt32 WideningWidening 可以。Yes. UInt32支援10個十進位數的有效位數;Single支援9。UInt32 supports 10 decimal digits of precision; Single supports 9.
UInt64 WideningWidening 可以。Yes. Int64支援20個十進位數的有效位數;Single支援9。Int64 supports 20 decimal digits of precision; Single supports 9.

``````using System;

public class Example
{
public static void Main()
{
dynamic[] values = { Byte.MinValue, Byte.MaxValue, Decimal.MinValue,
Decimal.MaxValue, Double.MinValue, Double.MaxValue,
Int16.MinValue, Int16.MaxValue, Int32.MinValue,
Int32.MaxValue, Int64.MinValue, Int64.MaxValue,
SByte.MinValue, SByte.MaxValue, UInt16.MinValue,
UInt16.MaxValue, UInt32.MinValue, UInt32.MaxValue,
UInt64.MinValue, UInt64.MaxValue };
float sngValue;
foreach (var value in values) {
if (value.GetType() == typeof(Decimal) ||
value.GetType() == typeof(Double))
sngValue = (float) value;
else
sngValue = value;
Console.WriteLine("{0} ({1}) --> {2:R} ({3})",
value, value.GetType().Name,
sngValue, sngValue.GetType().Name);
}
}
}
// The example displays the following output:
//       0 (Byte) --> 0 (Single)
//       255 (Byte) --> 255 (Single)
//       -79228162514264337593543950335 (Decimal) --> -7.92281625E+28 (Single)
//       79228162514264337593543950335 (Decimal) --> 7.92281625E+28 (Single)
//       -1.79769313486232E+308 (Double) --> -Infinity (Single)
//       1.79769313486232E+308 (Double) --> Infinity (Single)
//       -32768 (Int16) --> -32768 (Single)
//       32767 (Int16) --> 32767 (Single)
//       -2147483648 (Int32) --> -2.14748365E+09 (Single)
//       2147483647 (Int32) --> 2.14748365E+09 (Single)
//       -9223372036854775808 (Int64) --> -9.223372E+18 (Single)
//       9223372036854775807 (Int64) --> 9.223372E+18 (Single)
//       -128 (SByte) --> -128 (Single)
//       127 (SByte) --> 127 (Single)
//       0 (UInt16) --> 0 (Single)
//       65535 (UInt16) --> 65535 (Single)
//       0 (UInt32) --> 0 (Single)
//       4294967295 (UInt32) --> 4.2949673E+09 (Single)
//       0 (UInt64) --> 0 (Single)
//       18446744073709551615 (UInt64) --> 1.84467441E+19 (Single)
``````
``````Module Example
Public Sub Main()
Dim values() As Object = { Byte.MinValue, Byte.MaxValue, Decimal.MinValue,
Decimal.MaxValue, Double.MinValue, Double.MaxValue,
Int16.MinValue, Int16.MaxValue, Int32.MinValue,
Int32.MaxValue, Int64.MinValue, Int64.MaxValue,
SByte.MinValue, SByte.MaxValue, UInt16.MinValue,
UInt16.MaxValue, UInt32.MinValue, UInt32.MaxValue,
UInt64.MinValue, UInt64.MaxValue }
Dim sngValue As Single
For Each value In values
If value.GetType() = GetType(Double) Then
sngValue = CSng(value)
Else
sngValue = value
End If
Console.WriteLine("{0} ({1}) --> {2:R} ({3})",
value, value.GetType().Name,
sngValue, sngValue.GetType().Name)
Next
End Sub
End Module
' The example displays the following output:
'       0 (Byte) --> 0 (Single)
'       255 (Byte) --> 255 (Single)
'       -79228162514264337593543950335 (Decimal) --> -7.92281625E+28 (Single)
'       79228162514264337593543950335 (Decimal) --> 7.92281625E+28 (Single)
'       -1.79769313486232E+308 (Double) --> -Infinity (Single)
'       1.79769313486232E+308 (Double) --> Infinity (Single)
'       -32768 (Int16) --> -32768 (Single)
'       32767 (Int16) --> 32767 (Single)
'       -2147483648 (Int32) --> -2.14748365E+09 (Single)
'       2147483647 (Int32) --> 2.14748365E+09 (Single)
'       -9223372036854775808 (Int64) --> -9.223372E+18 (Single)
'       9223372036854775807 (Int64) --> 9.223372E+18 (Single)
'       -128 (SByte) --> -128 (Single)
'       127 (SByte) --> 127 (Single)
'       0 (UInt16) --> 0 (Single)
'       65535 (UInt16) --> 65535 (Single)
'       0 (UInt32) --> 0 (Single)
'       4294967295 (UInt32) --> 4.2949673E+09 (Single)
'       0 (UInt64) --> 0 (Single)
'       18446744073709551615 (UInt64) --> 1.84467441E+19 (Single)
``````

In addition, the Double values Double.NaN, Double.PositiveInfinity, and Double.NegativeInfinity covert to Single.NaN, Single.PositiveInfinity, and Single.NegativeInfinity, respectively.

Single值轉換Double成是擴輾轉換。The conversion of a Single value to a Double is a widening conversion. 如果Double類型沒有Single值的精確表示, 則轉換可能會導致失去有效位數。The conversion may result in a loss of precision if the Double type does not have a precise representation for the Single value.

Single值轉換為以外Double的任何基本數值資料類型的值是縮小轉換, 而且需要轉換運算子 (在中C#) 或轉換方法 (在 Visual Basic 中)。The conversion of a Single value to a value of any primitive numeric data type other than a Double is a narrowing conversion and requires a cast operator (in C#) or a conversion method (in Visual Basic). 在目標資料類型的範圍外的值 (由目標型別的`MinValue``MaxValue`屬性所定義), 其行為如下表所示。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.

Decimal OverflowException例外狀況,An OverflowException exception,

Single.NaN此外, Single.PositiveInfinity、和Single.NegativeInfinity會擲OverflowException回以進行已檢查內容中的整數轉換, 但這些值會在轉換成未檢查內容中的整數時溢位。In addition, Single.NaN, Single.PositiveInfinity, and Single.NegativeInfinity throw an OverflowException for conversions to integers in a checked context, but these values overflow when converted to integers in an unchecked context. 針對轉換為Decimal, 它們一律會OverflowException擲回。For conversions to Decimal, they always throw an OverflowException. 針對轉換為Double, 它們會分別Double.NaN轉換Double.PositiveInfinity為、 Double.NegativeInfinity和。For conversions to Double, they convert to Double.NaN, Double.PositiveInfinity, and Double.NegativeInfinity, respectively.

``````using System;

public class Example
{
public static void Main()
{
float[] values = { Single.MinValue, -67890.1234f, -12345.6789f,
12345.6789f, 67890.1234f, Single.MaxValue,
Single.NaN, Single.PositiveInfinity,
Single.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);
}

Double dblValue = value;
Console.WriteLine("{0} ({1}) --> {2} ({3})",
value, value.GetType().Name,
dblValue, dblValue.GetType().Name);
Console.WriteLine();
}
}
}
}
// The example displays the following output for conversions performed
// in a checked context:
//       Unable to convert -3.402823E+38 to Int64.
//       Unable to convert -3.402823E+38 to UInt64.
//       Unable to convert -3.402823E+38 to Decimal.
//       -3.402823E+38 (Single) --> -3.40282346638529E+38 (Double)
//
//       -67890.13 (Single) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
//       Unable to convert -67890.13 to UInt64.
//       -67890.13 (Single) --> -67890.12 (Decimal)
//       -67890.13 (Single) --> -67890.125 (Double)
//
//       -12345.68 (Single) --> -12345 (0xFFFFFFFFFFFFCFC7) (Int64)
//       Unable to convert -12345.68 to UInt64.
//       -12345.68 (Single) --> -12345.68 (Decimal)
//       -12345.68 (Single) --> -12345.6787109375 (Double)
//
//       12345.68 (Single) --> 12345 (0x0000000000003039) (Int64)
//       12345.68 (Single) --> 12345 (0x0000000000003039) (UInt64)
//       12345.68 (Single) --> 12345.68 (Decimal)
//       12345.68 (Single) --> 12345.6787109375 (Double)
//
//       67890.13 (Single) --> 67890 (0x0000000000010932) (Int64)
//       67890.13 (Single) --> 67890 (0x0000000000010932) (UInt64)
//       67890.13 (Single) --> 67890.12 (Decimal)
//       67890.13 (Single) --> 67890.125 (Double)
//
//       Unable to convert 3.402823E+38 to Int64.
//       Unable to convert 3.402823E+38 to UInt64.
//       Unable to convert 3.402823E+38 to Decimal.
//       3.402823E+38 (Single) --> 3.40282346638529E+38 (Double)
//
//       Unable to convert NaN to Int64.
//       Unable to convert NaN to UInt64.
//       Unable to convert NaN to Decimal.
//       NaN (Single) --> NaN (Double)
//
//       Unable to convert Infinity to Int64.
//       Unable to convert Infinity to UInt64.
//       Unable to convert Infinity to Decimal.
//       Infinity (Single) --> Infinity (Double)
//
//       Unable to convert -Infinity to Int64.
//       Unable to convert -Infinity to UInt64.
//       Unable to convert -Infinity to Decimal.
//       -Infinity (Single) --> -Infinity (Double)
// The example displays the following output for conversions performed
// in an unchecked context:
//       -3.402823E+38 (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       -3.402823E+38 (Single) --> 9223372036854775808 (0x8000000000000000) (UInt64)
//       Unable to convert -3.402823E+38 to Decimal.
//       -3.402823E+38 (Single) --> -3.40282346638529E+38 (Double)
//
//       -67890.13 (Single) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
//       -67890.13 (Single) --> 18446744073709483726 (0xFFFFFFFFFFFEF6CE) (UInt64)
//       -67890.13 (Single) --> -67890.12 (Decimal)
//       -67890.13 (Single) --> -67890.125 (Double)
//
//       -12345.68 (Single) --> -12345 (0xFFFFFFFFFFFFCFC7) (Int64)
//       -12345.68 (Single) --> 18446744073709539271 (0xFFFFFFFFFFFFCFC7) (UInt64)
//       -12345.68 (Single) --> -12345.68 (Decimal)
//       -12345.68 (Single) --> -12345.6787109375 (Double)
//
//       12345.68 (Single) --> 12345 (0x0000000000003039) (Int64)
//       12345.68 (Single) --> 12345 (0x0000000000003039) (UInt64)
//       12345.68 (Single) --> 12345.68 (Decimal)
//       12345.68 (Single) --> 12345.6787109375 (Double)
//
//       67890.13 (Single) --> 67890 (0x0000000000010932) (Int64)
//       67890.13 (Single) --> 67890 (0x0000000000010932) (UInt64)
//       67890.13 (Single) --> 67890.12 (Decimal)
//       67890.13 (Single) --> 67890.125 (Double)
//
//       3.402823E+38 (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       3.402823E+38 (Single) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert 3.402823E+38 to Decimal.
//       3.402823E+38 (Single) --> 3.40282346638529E+38 (Double)
//
//       NaN (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       NaN (Single) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert NaN to Decimal.
//       NaN (Single) --> NaN (Double)
//
//       Infinity (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       Infinity (Single) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert Infinity to Decimal.
//       Infinity (Single) --> Infinity (Double)
//
//       -Infinity (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       -Infinity (Single) --> 9223372036854775808 (0x8000000000000000) (UInt64)
//       Unable to convert -Infinity to Decimal.
//       -Infinity (Single) --> -Infinity (Double)
``````
``````Module Example
Public Sub Main()
Dim values() As Single = { Single.MinValue, -67890.1234, -12345.6789,
12345.6789, 67890.1234, Single.MaxValue,
Single.NaN, Single.PositiveInfinity,
Single.NegativeInfinity }
For Each value In values
Try
Dim lValue As Long = 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

Dim dblValue As Double = value
Console.WriteLine("{0} ({1}) --> {2} ({3})",
value, value.GetType().Name,
dblValue, dblValue.GetType().Name)
Console.WriteLine()
Next
End Sub
End Module
' The example displays the following output for conversions performed
' in a checked context:
'       Unable to convert -3.402823E+38 to Int64.
'       Unable to convert -3.402823E+38 to UInt64.
'       Unable to convert -3.402823E+38 to Decimal.
'       -3.402823E+38 (Single) --> -3.40282346638529E+38 (Double)
'
'       -67890.13 (Single) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
'       Unable to convert -67890.13 to UInt64.
'       -67890.13 (Single) --> -67890.12 (Decimal)
'       -67890.13 (Single) --> -67890.125 (Double)
'
'       -12345.68 (Single) --> -12346 (0xFFFFFFFFFFFFCFC6) (Int64)
'       Unable to convert -12345.68 to UInt64.
'       -12345.68 (Single) --> -12345.68 (Decimal)
'       -12345.68 (Single) --> -12345.6787109375 (Double)
'
'       12345.68 (Single) --> 12346 (0x000000000000303A) (Int64)
'       12345.68 (Single) --> 12346 (0x000000000000303A) (UInt64)
'       12345.68 (Single) --> 12345.68 (Decimal)
'       12345.68 (Single) --> 12345.6787109375 (Double)
'
'       67890.13 (Single) --> 67890 (0x0000000000010932) (Int64)
'       67890.13 (Single) --> 67890 (0x0000000000010932) (UInt64)
'       67890.13 (Single) --> 67890.12 (Decimal)
'       67890.13 (Single) --> 67890.125 (Double)
'
'       Unable to convert 3.402823E+38 to Int64.
'       Unable to convert 3.402823E+38 to UInt64.
'       Unable to convert 3.402823E+38 to Decimal.
'       3.402823E+38 (Single) --> 3.40282346638529E+38 (Double)
'
'       Unable to convert NaN to Int64.
'       Unable to convert NaN to UInt64.
'       Unable to convert NaN to Decimal.
'       NaN (Single) --> NaN (Double)
'
'       Unable to convert Infinity to Int64.
'       Unable to convert Infinity to UInt64.
'       Unable to convert Infinity to Decimal.
'       Infinity (Single) --> Infinity (Double)
'
'       Unable to convert -Infinity to Int64.
'       Unable to convert -Infinity to UInt64.
'       Unable to convert -Infinity to Decimal.
'       -Infinity (Single) --> -Infinity (Double)
' The example displays the following output for conversions performed
' in an unchecked context:
'       -3.402823E+38 (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       -3.402823E+38 (Single) --> 9223372036854775808 (0x8000000000000000) (UInt64)
'       Unable to convert -3.402823E+38 to Decimal.
'       -3.402823E+38 (Single) --> -3.40282346638529E+38 (Double)
'
'       -67890.13 (Single) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
'       -67890.13 (Single) --> 18446744073709483726 (0xFFFFFFFFFFFEF6CE) (UInt64)
'       -67890.13 (Single) --> -67890.12 (Decimal)
'       -67890.13 (Single) --> -67890.125 (Double)
'
'       -12345.68 (Single) --> -12346 (0xFFFFFFFFFFFFCFC6) (Int64)
'       -12345.68 (Single) --> 18446744073709539270 (0xFFFFFFFFFFFFCFC6) (UInt64)
'       -12345.68 (Single) --> -12345.68 (Decimal)
'       -12345.68 (Single) --> -12345.6787109375 (Double)
'
'       12345.68 (Single) --> 12346 (0x000000000000303A) (Int64)
'       12345.68 (Single) --> 12346 (0x000000000000303A) (UInt64)
'       12345.68 (Single) --> 12345.68 (Decimal)
'       12345.68 (Single) --> 12345.6787109375 (Double)
'
'       67890.13 (Single) --> 67890 (0x0000000000010932) (Int64)
'       67890.13 (Single) --> 67890 (0x0000000000010932) (UInt64)
'       67890.13 (Single) --> 67890.12 (Decimal)
'       67890.13 (Single) --> 67890.125 (Double)
'
'       3.402823E+38 (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       3.402823E+38 (Single) --> 0 (0x0000000000000000) (UInt64)
'       Unable to convert 3.402823E+38 to Decimal.
'       3.402823E+38 (Single) --> 3.40282346638529E+38 (Double)
'
'       NaN (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       NaN (Single) --> 0 (0x0000000000000000) (UInt64)
'       Unable to convert NaN to Decimal.
'       NaN (Single) --> NaN (Double)
'
'       Infinity (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       Infinity (Single) --> 0 (0x0000000000000000) (UInt64)
'       Unable to convert Infinity to Decimal.
'       Infinity (Single) --> Infinity (Double)
'
'       -Infinity (Single) --> -9223372036854775808 (0x8000000000000000) (Int64)
'       -Infinity (Single) --> 9223372036854775808 (0x8000000000000000) (UInt64)
'       Unable to convert -Infinity to Decimal.
'       -Infinity (Single) --> -Infinity (Double)
``````

### 浮點功能Floating-point functionality

Single結構和相關類型提供執行下列作業分類的方法:The Single structure and related types provide methods to perform the following categories of operations:

• 值的比較Comparison of values. 您可以呼叫Equals方法來判斷兩個Single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 Single values are equal, or the CompareTo method to determine the relationship between two values.

Single結構也支援一組完整的比較運算子。The Single structure also supports a complete set of comparison operators. 例如, 您可以測試是否相等或不等比較, 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 value. 如果其中一個運算元是Double, 則會DoubleSingle將值轉換成, 再執行比較。If one of the operands is a Double, the Single value is converted to a Double before performing the comparison. 如果其中一個運算元是整數類資料類型, 則會Single先將它轉換成, 再執行比較。If one of the operands is an integral type, it is converted to a Single before performing the comparison. 雖然這些是擴輾轉換, 但它們可能會遺失有效位數。Although these are widening conversions, they may involve a loss of precision.

警告

由於精確度的差異, 您預期Single相等的兩個值可能會變成不相等, 這會影響比較的結果。Because of differences in precision, two Single 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Single值的詳細資訊, 請參閱測試相等一節。See the Testing for equality section for more information about comparing two Single values.

您也可以IsNaN呼叫、 IsInfinityIsPositiveInfinityIsNegativeInfinity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. 一般算數運算 (例如加法、減法、乘法和除法) 是由語言編譯器和一般中繼語言 (CIL) 指示所執行, 而Single不是透過方法。Common arithmetic operations such as addition, subtraction, multiplication, and division are implemented by language compilers and Common Intermediate Language (CIL) instructions rather than by Single methods. 如果數學運算中的Double另一個運算元是Single , 則會Double先將轉換成, 然後再執行作業, 而作業Double的結果也是值。If the other operand in a mathematical operation is a Double, the Single is converted to a Double before performing the operation, and the result of the operation is also a Double value. 如果另一個運算元是整數類資料類型, 則會Single先將它轉換為, 然後再執行作業, 而作業的結果Single也是值。If the other operand is an integral type, it is converted to a Single before performing the operation, and the result of the operation is also a Single value.

您可以藉由呼叫`static`類別中的System.Math (`Shared`在 Visual Basic 中) 方法, 來執行其他數學運算。You can perform other mathematical operations by calling `static` (`Shared` in Visual Basic) methods in the System.Math class. 這些包括常用於算術的其他方法 (例如Math.AbsMath.Sign Math.Sin Math.Sqrt和)、geometry (例如Math.Cos和), 以及微積分 (例如Math.Log)。These include 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). 在所有情況下, Single值都會轉換Double成。In all cases, the Single value is converted to a Double.

您也可以在Single值中操作個別位。You can also manipulate the individual bits in a Single value. BitConverter.GetBytes(Single)方法會在位元組陣列中傳回其位模式。The BitConverter.GetBytes(Single) method returns its bit pattern in a byte array. 藉由將該位元組陣列傳遞BitConverter.ToInt32給方法, 您也可以在Single 32 位整數中保留值的位模式。By passing that byte array to the BitConverter.ToInt32 method, you can also preserve the Single value's bit pattern in a 32-bit integer.

• 進位Rounding. 進位通常用來做為減少因浮點標記法和精確度問題而造成之值差異的技術。Rounding is often used as a technique for reducing the impact of differences between values caused by problems of floating-point representation and precision. 您可以藉由Single Math.Round呼叫方法來舍入值。You can round a Single value by calling the Math.Round method. 不過, 請注意Single , 在呼叫方法Double之前, 值會轉換為, 而轉換可能牽涉到遺失精確度。However, note that the Single value is converted to a Double before the method is called, and the conversion can involve a loss of precision.

• 格式Formatting. 您可以藉由Single ToString呼叫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 Single 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的字串標記法的詳細資訊, 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. 您可以藉由Single Parse呼叫或TryParse方法, 將浮點值的字串表示轉換為值。You can convert the string representation of a floating-point value to a Single value by calling the Parse or TryParse method. 如果剖析作業失敗, Parse方法會擲回例外狀況, TryParse而方法`false`會傳回。If the parse operation fails, the Parse method throws an exception, whereas the TryParse method returns `false`.

• 類型轉換Type conversion. 結構會提供介面的明確介面實作為IConvertible , 支援在任何兩個標準 .NET Framework 資料類型之間進行轉換。 SingleThe Single structure provides an explicit interface implementation for the IConvertible interface, which supports conversion between any two standard .NET Framework data types. 除了將轉換DoubleSingle值以外, 語言編譯器也支援所有其他標準數數值型別之值的隱含轉換。Language compilers also support the implicit conversion of values for all other standard numeric types except for the conversion of Double to Single values. 將以外的任何標準數數值型別Double Single的值轉換為擴輾轉換, 而且不需要使用轉換運算子或轉換方法。Conversion of a value of any standard numeric type other than a Double to a Single is a widening conversion and does not require the use of a casting operator or conversion method.

不過, 32 位和64位整數值的轉換可能牽涉到精確度遺失。However, conversion of 32-bit and 64-bit integer values can involve a loss of precision. 下表列出32位、64位和Double類型的有效位數差異:The following table lists the differences in precision for 32-bit, 64-bit, and Double types:

類型Type 最大有效位數 (以十進位數為准)Maximum precision (in decimal digits) 內部有效位數 (以十進位數為准)Internal precision (in decimal digits)
Double 1515 1717
Int32 and UInt32 1010 1010
Int64 and UInt64 1919 1919
Single 77 99

精確度的問題最常影響Single轉換成Double值的值。The 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Double單精確度浮點值。In the following example, two values produced by identical division operations are unequal, because one of the values is a single-precision floating point value that is converted to a Double.

``````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
``````

## 欄位

 Epsilon Epsilon Epsilon Epsilon 代表大於零的最小正 Single 值。Represents the smallest positive Single value that is greater than zero. 這個欄位是常數。This field is constant. MaxValue MaxValue MaxValue MaxValue 代表 Single 最大的可能值。Represents the largest possible value of Single. 這個欄位是常數。This field is constant. MinValue MinValue MinValue MinValue 代表 Single 最小的可能值。Represents the smallest possible value of Single. 這個欄位是常數。This field is constant. NaN NaN NaN NaN 代表非數值 (`NaN`)。Represents not a number (`NaN`). 這個欄位是常數。This field is constant. NegativeInfinity NegativeInfinity NegativeInfinity NegativeInfinity 表示負無限大。Represents negative infinity. 這個欄位是常數。This field is constant. PositiveInfinity PositiveInfinity PositiveInfinity PositiveInfinity 表示正無限大。Represents positive infinity. 這個欄位是常數。This field is constant.

## 運算子

 Equality(Single, Single) Equality(Single, Single) Equality(Single, Single) Equality(Single, Single) 傳回值，這個值表示兩個指定的 Single 值是否相等。Returns a value that indicates whether two specified Single values are equal. GreaterThan(Single, Single) GreaterThan(Single, Single) GreaterThan(Single, Single) GreaterThan(Single, Single) 傳回值，這個值表示指定的 Single 值是否大於另一個指定的 Single 值。Returns a value that indicates whether a specified Single value is greater than another specified Single value. GreaterThanOrEqual(Single, Single) GreaterThanOrEqual(Single, Single) GreaterThanOrEqual(Single, Single) GreaterThanOrEqual(Single, Single) 傳回值，這個值表示指定的 Single 值是否大於或等於另一個指定的 Single 值。Returns a value that indicates whether a specified Single value is greater than or equal to another specified Single value. Inequality(Single, Single) Inequality(Single, Single) Inequality(Single, Single) Inequality(Single, Single) 傳回值，這個值表示兩個指定的 Single 值是否不相等。Returns a value that indicates whether two specified Single values are not equal. LessThan(Single, Single) LessThan(Single, Single) LessThan(Single, Single) LessThan(Single, Single) 傳回值，這個值表示指定的 Single 值是否小於另一個指定的 Single 值。Returns a value that indicates whether a specified Single value is less than another specified Single value. LessThanOrEqual(Single, Single) LessThanOrEqual(Single, Single) LessThanOrEqual(Single, Single) LessThanOrEqual(Single, Single) 傳回值，這個值表示指定的 Single 值是否小於或等於另一個指定的 Single 值。Returns a value that indicates whether a specified Single value is less than or equal to another specified Single value.

## 明確介面實作

 IComparable.CompareTo(Object) IComparable.CompareTo(Object) IComparable.CompareTo(Object) IComparable.CompareTo(Object) IConvertible.GetTypeCode() IConvertible.GetTypeCode() IConvertible.GetTypeCode() IConvertible.GetTypeCode() IConvertible.ToBoolean(IFormatProvider) IConvertible.ToBoolean(IFormatProvider) IConvertible.ToBoolean(IFormatProvider) 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) IConvertible.ToByte(IFormatProvider) IConvertible.ToByte(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) IConvertible.ToChar(IFormatProvider) IConvertible.ToChar(IFormatProvider) IConvertible.ToChar(IFormatProvider) 不支援這個轉換。This conversion is not supported. 嘗試使用這個方法會擲回 InvalidCastException。Attempting to use this method throws an InvalidCastException. IConvertible.ToDateTime(IFormatProvider) IConvertible.ToDateTime(IFormatProvider) IConvertible.ToDateTime(IFormatProvider) IConvertible.ToDateTime(IFormatProvider) 不支援這個轉換。This conversion is not supported. 嘗試使用這個方法會擲回 InvalidCastException。Attempting to use this method throws an InvalidCastException. IConvertible.ToDecimal(IFormatProvider) IConvertible.ToDecimal(IFormatProvider) IConvertible.ToDecimal(IFormatProvider) 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) IConvertible.ToDouble(IFormatProvider) IConvertible.ToDouble(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) IConvertible.ToInt16(IFormatProvider) IConvertible.ToInt16(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) IConvertible.ToInt32(IFormatProvider) IConvertible.ToInt32(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) IConvertible.ToInt64(IFormatProvider) IConvertible.ToInt64(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) IConvertible.ToSByte(IFormatProvider) IConvertible.ToSByte(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) IConvertible.ToSingle(IFormatProvider) IConvertible.ToSingle(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) IConvertible.ToType(Type, IFormatProvider) IConvertible.ToType(Type, 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) IConvertible.ToUInt16(IFormatProvider) IConvertible.ToUInt16(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) IConvertible.ToUInt32(IFormatProvider) IConvertible.ToUInt32(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) IConvertible.ToUInt64(IFormatProvider) IConvertible.ToUInt64(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).