Single.CompareTo 方法

定義

比較這個執行個體和指定的物件或另一個 Single 執行個體,並且傳回整數,這個整數表示這個執行個體的值是否小於、等於或大於所指定之物件或另一個 Single 執行個體的值。Compares this instance to a specified object or to another Single instance 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 or the other Single instance.

多載

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.

CompareTo(Single)

比較這個執行個體與指定的單精確度浮點數,並且傳回整數,這個整數表示這個執行個體的值是小於、等於或大於指定的單精確度浮點數。Compares this instance to a specified single-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 single-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.

public:
 virtual int CompareTo(System::Object ^ value);
public int CompareTo (object value);
abstract member CompareTo : obj -> int
override this.CompareTo : obj -> int
Public Function CompareTo (value As Object) As Integer

參數

value
Object

要比較的物件或 nullAn object to compare, or null.

傳回

帶正負號的數字,其指出這個執行個體與 value 的相對值。A signed number indicating the relative values of this instance and value.

傳回值Return Value 描述Description
小於零 (0)Less than zero 這個執行個體小於 valueThis instance is less than value. -或--or- 這個執行個體是非數字 (NaN),且 value 是數字。This instance is not a number (NaN) and value is a number.
Zero 這個執行個體等於 valueThis instance is equal to value. -或--or- 這個執行個體和值皆為非數字 (NaN)、PositiveInfinityNegativeInfinityThis instance and value are both not a number (NaN), PositiveInfinity, or NegativeInfinity.
大於零 (0)Greater than zero 這個執行個體大於 valueThis instance is greater than value. -或--or- 這個執行個體是數字,且 value 為非數字 (NaN)。This instance is a number and value is not a number (NaN). -或--or- valuenullvalue is null.

實作

例外狀況

value 不是 Singlevalue is not a Single.

範例

下列程式碼範例示範 CompareTo 方法。The following code example demonstrates the CompareTo method.

obj1 = (Single)450;

if ( a.CompareTo( obj1 ) < 0 )
{
   Console::WriteLine( " {0} is less than {1}.", a, obj1 );
}

if ( a.CompareTo( obj1 ) > 0 )
{
   Console::WriteLine( " {0} is greater than {1}.", a, obj1 );
}

if ( a.CompareTo( obj1 ) == 0 )
{
   Console::WriteLine( " {0} equals {1}.", a, obj1 );
}
obj1 = (Single)450;

if (a.CompareTo(obj1) < 0)
{
    Console.WriteLine("{0} is less than {1}.", a.ToString(), obj1.ToString());
}

if (a.CompareTo(obj1) > 0)
{
    Console.WriteLine("{0} is greater than {1}.", a.ToString(), obj1.ToString());
}

if (a.CompareTo(obj1) == 0)
{
    Console.WriteLine("{0} equals {1}.", a.ToString(), obj1.ToString());
}
Obj1 = CType(450, Single)

If A.CompareTo(Obj1) < 0 Then
    Console.WriteLine(A.ToString() + " is less than " + Obj1.ToString() + ".")
End If

If (A.CompareTo(Obj1) > 0) Then
    Console.WriteLine(A.ToString() + " is greater than " + Obj1.ToString() + ".")
End If

If (A.CompareTo(Obj1) = 0) Then
    Console.WriteLine(A.ToString() + " equals " + Obj1.ToString() + ".")
End If

備註

value 參數必須 nullSingle的實例。否則,就會擲回例外狀況。The value parameter must be null or an instance of Single; otherwise, an exception is thrown. 任何 Single的實例(不論其值為何)都會視為大於 nullAny instance of Single, regardless of its value, is considered greater than null.

值必須完全相同,才能視為相等。Values must be identical to be considered equal. 特別是當浮點值相依于多個數學運算時,通常會失去精確度,而且其值幾乎完全相同,但不包括其最小有效位數。Particularly when floating-point values depend on multiple mathematical operations, it is common for them to lose precision and for their values to be nearly identical except for their least significant digits. 因此,CompareTo 方法的傳回值,有時可能會感到驚訝。Because of this, the return value of the CompareTo method may seem surprising at times. 例如,以特定值乘以後面加上相同值的除法,應該會產生原始值,但在下列範例中,計算值會變成大於原始值。For example, multiplication by a particular value followed by division by the same value should produce the original value, but in the following example, the computed value turns out to be greater than the original value. 使用 "R"標準數值格式字串來顯示這兩個值的所有有效位數,表示計算值與其最小有效位數中的原始值不同。Showing all significant digits of the two values by using the "R" standard numeric format string indicates that the computed value differs from the original value in its least significant digits. 如需處理這類比較的相關資訊,請參閱 Equals(Single) 方法的「備註」一節。For information about handling such comparisons, see the Remarks section of the Equals(Single) method.

using System;

public class Example
{
   public static void Main()
   {
       float value1 = 16.5457f;
       float operand = 3.8899982f;
       object value2 = value1 * operand / operand;
       Console.WriteLine("Comparing {0} and {1}: {2}\n",
                         value1, value2, value1.CompareTo(value2));
       Console.WriteLine("Comparing {0:R} and {1:R}: {2}",
                         value1, value2, value1.CompareTo(value2));
   }
}
// The example displays the following output:
//       Comparing 16.5457 and 16.5457: -1
//       
//       Comparing 16.5457 and 16.545702: -1
Module Example
   Public Sub Main()
       Dim value1 As Single = 16.5457
       Dim value2 As Object = value1 * CSng(3.8899982) / CSng(3.8899982)
       Console.WriteLine("Comparing {0} and {1}: {2}",
                         value1, value2, value1.CompareTo(value2))
       Console.WriteLine()
       Console.WriteLine("Comparing {0:R} and {1:R}: {2}",
                         value1, value2, value1.CompareTo(value2))
   End Sub
End Module
' The example displays the following output:
'       Comparing 16.5457 and 16.5457: -1
'       
'       Comparing 16.5457 and 16.545702: -1

這個方法會實作為支援 IComparable 介面。This method is implemented to support the IComparable interface. 請注意,雖然 NaN 不會被視為等於另一個 NaN (甚至是其本身),但 IComparable 介面會要求 A.CompareTo(A) 傳回零。Note that, although a NaN is not considered to be equal to another NaN (even itself), the IComparable interface requires that A.CompareTo(A) return zero.

比較的有效位數Precision in Comparisons

超出記載精確度的浮點數精確度,是 .NET Framework 的實值和版本所特有。The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework. 因此,兩個特定數位的比較可能會在 .NET Framework 版本之間變更,因為數位的內部標記法的精確度可能會改變。Consequently, a comparison of two particular numbers might change between versions of the .NET Framework because the precision of the numbers' internal representation might change.

另請參閱

CompareTo(Single)

比較這個執行個體與指定的單精確度浮點數,並且傳回整數,這個整數表示這個執行個體的值是小於、等於或大於指定的單精確度浮點數。Compares this instance to a specified single-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 single-precision floating-point number.

public:
 virtual int CompareTo(float value);
public int CompareTo (float value);
abstract member CompareTo : single -> int
override this.CompareTo : single -> int
Public Function CompareTo (value As Single) As Integer

參數

value
Single

要比較的單精確度浮點數。A single-precision floating-point number to compare.

傳回

帶正負號的數字,其指出這個執行個體與 value 的相對值。A signed number indicating the relative values of this instance and value.

傳回值Return Value 描述Description
小於零 (0)Less than zero 這個執行個體小於 valueThis instance is less than value. -或--or- 這個執行個體是非數字 (NaN),且 value 是數字。This instance is not a number (NaN) and value is a number.
Zero 這個執行個體等於 valueThis instance is equal to value. -或--or- 這個執行個體和 value 都不會是數字 (NaN)、PositiveInfinityNegativeInfinityBoth this instance and value are not a number (NaN), PositiveInfinity, or NegativeInfinity.
大於零 (0)Greater than zero 這個執行個體大於 valueThis instance is greater than value. -或--or- 這個執行個體是數字,且 value 為非數字 (NaN)。This instance is a number and value is not a number (NaN).

實作

範例

下列程式碼範例將示範數個值和參考型別之 CompareTo 方法的泛型和非泛型版本。The following code example demonstrates generic and nongeneric versions of the CompareTo method for several value and reference types.

// This example demonstrates the two versions of the 
// CompareTo method for several base types.
// The general version takes a parameter of type Object, while the specific
// version takes a type-specific parameter, such as Boolean, Int32, or Double.
using namespace System;

void Show( String^ caption, Object^ var1, Object^ var2, int resultGeneric, int resultNonGeneric )
{
   String^ relation;
   Console::Write( caption );
   if ( resultGeneric == resultNonGeneric )
   {
      if ( resultGeneric < 0 )
            relation = "less than";
      else
      if ( resultGeneric > 0 )
            relation = "greater than";
      else
            relation = "equal to";
      Console::WriteLine( "{0} is {1} {2}", var1, relation, var2 );
   }
   // The following condition will never occur because the generic and non-generic
   // CompareTo methods are equivalent.
   else
   {
      Console::WriteLine( "Generic CompareTo = {0}; non-generic CompareTo = {1}", resultGeneric, resultNonGeneric );
   }
}

int main()
{
   String^ nl = Environment::NewLine;
   String^ msg = "{0}The following is the result of using the generic and non-generic{0}"
   "versions of the CompareTo method for several base types:{0}";
   Object^ obj; // An Object used to insure CompareTo(Object) is called.

   DateTime now = DateTime::Now;
   
   // Time span = 11 days, 22 hours, 33 minutes, 44 seconds
   TimeSpan tsX = TimeSpan(11,22,33,44);
   
   // Version = 1.2.333.4
   Version^ versX = gcnew Version(  "1.2.333.4" );
   
   // Guid = CA761232-ED42-11CE-BACD-00AA0057B223
   Guid guidX = Guid( "{CA761232-ED42-11CE-BACD-00AA0057B223}");
   Boolean a1 = true,a2 = true;
   Byte b1 = 1,b2 = 1;
   Int16 c1 = -2,c2 = 2;
   Int32 d1 = 3,d2 = 3;
   Int64 e1 = 4,e2 = -4;
   Decimal f1 = Decimal(-5.5), f2 = Decimal(5.5);
   Single g1 = 6.6f,g2 = 6.6f;
   Double h1 = 7.7,h2 = -7.7;
   Char i1 = 'A',i2 = 'A';
   String^ j1 = "abc", ^j2 = "abc";
   DateTime k1 = now,k2 = now;
   TimeSpan l1 = tsX,l2 = tsX;
   Version^ m1 = versX, ^m2 = gcnew Version(  "2.0" );
   Guid n1 = guidX,n2 = guidX;
   
   // The following types are not CLS-compliant.
   SByte w1 = 8,w2 = 8;
   UInt16 x1 = 9,x2 = 9;
   UInt32 y1 = 10,y2 = 10;
   UInt64 z1 = 11,z2 = 11;
   
   //
   Console::WriteLine( msg, nl );
   try
   {
      Show( "Boolean: ", a1, a2, a1.CompareTo( a2 ), a1.CompareTo( a2 ) );
      Show( "Byte:    ", b1, b2, b1.CompareTo( b2 ), b1.CompareTo( b2 ) );
      Show( "Int16:   ", c1, c2, c1.CompareTo( c2 ), c1.CompareTo( c2 ) );
      Show( "Int32:   ", d1, d2, d1.CompareTo( d2 ), d1.CompareTo( d2 ) );
      Show( "Int64:   ", e1, e2, e1.CompareTo( e2 ), e1.CompareTo( e2 ) );
      Show( "Decimal: ", f1, f2, f1.CompareTo( f2 ), f1.CompareTo( f2 ) );
      Show( "Single:  ", g1, g2, g1.CompareTo( g2 ), g1.CompareTo( g2 ) );
      Show( "Double:  ", h1, h2, h1.CompareTo( h2 ), h1.CompareTo( h2 ) );
      Show( "Char:    ", i1, i2, i1.CompareTo( i2 ), i1.CompareTo( i2 ) );
      
      // Use an anonymous object to hide the String object.
      obj = j2;
      Show( "String:  ", j1, j2, j1->CompareTo( j2 ), j1->CompareTo( obj ) );
      Show( "DateTime:", k1, k2, k1.CompareTo( k2 ), k1.CompareTo( k2 ) );
      Show(  "TimeSpan: ", l1, l2, l1.CompareTo( l2 ), l1.CompareTo( l2 ) );
      
      // Use an anonymous object to hide the Version object.
      obj = m2;
      Show(  "Version:  ", m1, m2, m1->CompareTo( m2 ), m1->CompareTo( obj ) );
      Show(  "Guid:     ", n1, n2, n1.CompareTo( n2 ), n1.CompareTo( n2 ) );
      
      //
      Console::WriteLine( "{0}The following types are not CLS-compliant:", nl );
      Show( "SByte:   ", w1, w2, w1.CompareTo( w2 ), w1.CompareTo( w2 ) );
      Show( "UInt16:  ", x1, x2, x1.CompareTo( x2 ), x1.CompareTo( x2 ) );
      Show( "UInt32:  ", y1, y2, y1.CompareTo( y2 ), y1.CompareTo( y2 ) );
      Show( "UInt64:  ", z1, z2, z1.CompareTo( z2 ), z1.CompareTo( z2 ) );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( e );
   }

}
//     This example displays the following output:
//     
//     The following is the result of using the generic and non-generic versions of the
//     CompareTo method for several base types:
//     
//     Boolean:  True is equal to True
//     Byte:     1 is equal to 1
//     Int16:    -2 is less than 2
//     Int32:    3 is equal to 3
//     Int64:    4 is greater than -4
//     Decimal:  -5.5 is less than 5.5
//     Single:   6.6 is equal to 6.6
//     Double:   7.7 is greater than -7.7
//     Char:     A is equal to A
//     String:   abc is equal to abc
//     DateTime: 12/1/2003 5:37:46 PM is equal to 12/1/2003 5:37:46 PM
//     TimeSpan: 11.22:33:44 is equal to 11.22:33:44
//     Version:  1.2.333.4 is less than 2.0
//     Guid:     ca761232-ed42-11ce-bacd-00aa0057b223 is equal to ca761232-ed42-11ce-bacd-00
//     aa0057b223
//     
//     The following types are not CLS-compliant:
//     SByte:    8 is equal to 8
//     UInt16:   9 is equal to 9
//     UInt32:   10 is equal to 10
//     UInt64:   11 is equal to 11
// This example demonstrates the generic and non-generic versions of the 
// CompareTo method for several base types.
// The non-generic version takes a parameter of type Object, while the generic
// version takes a type-specific parameter, such as Boolean, Int32, or Double.

using System;

class Sample 
{
    public static void Main() 
    {
    string    nl = Environment.NewLine;
    string    msg = "{0}The following is the result of using the generic and non-generic{0}" +
                    "versions of the CompareTo method for several base types:{0}";

    DateTime  now = DateTime.Now;
// Time span = 11 days, 22 hours, 33 minutes, 44 seconds
    TimeSpan  tsX = new TimeSpan(11, 22, 33, 44); 
// Version = 1.2.333.4
    Version   versX = new Version("1.2.333.4");  
// Guid = CA761232-ED42-11CE-BACD-00AA0057B223
    Guid      guidX = new Guid("{CA761232-ED42-11CE-BACD-00AA0057B223}");

    Boolean  a1 = true,  a2 = true;
    Byte     b1 = 1,     b2 = 1;
    Int16    c1 = -2,    c2 = 2;
    Int32    d1 = 3,     d2 = 3;
    Int64    e1 = 4,     e2 = -4;
    Decimal  f1 = -5.5m, f2 = 5.5m;
    Single   g1 = 6.6f,  g2 = 6.6f;
    Double   h1 = 7.7d,  h2 = -7.7d;
    Char     i1 = 'A',   i2 = 'A';
    String   j1 = "abc", j2 = "abc";
    DateTime k1 = now,   k2 = now;
    TimeSpan l1 = tsX,   l2 = tsX;
    Version  m1 = versX, m2 = new Version("2.0");
    Guid     n1 = guidX, n2 = guidX;

// The following types are not CLS-compliant.
    SByte    w1 = 8,     w2 = 8;
    UInt16   x1 = 9,     x2 = 9;
    UInt32   y1 = 10,    y2 = 10;
    UInt64   z1 = 11,    z2 = 11;
//
    Console.WriteLine(msg, nl);
    try 
        {
// The second and third Show method call parameters are automatically boxed because
// the second and third Show method declaration arguments expect type Object.

        Show("Boolean:  ", a1, a2, a1.CompareTo(a2), a1.CompareTo((Object)a2));
        Show("Byte:     ", b1, b2, b1.CompareTo(b2), b1.CompareTo((Object)b2));
        Show("Int16:    ", c1, c2, c1.CompareTo(c2), c1.CompareTo((Object)c2));
        Show("Int32:    ", d1, d2, d1.CompareTo(d2), d1.CompareTo((Object)d2));
        Show("Int64:    ", e1, e2, e1.CompareTo(e2), e1.CompareTo((Object)e2));
        Show("Decimal:  ", f1, f2, f1.CompareTo(f2), f1.CompareTo((Object)f2));
        Show("Single:   ", g1, g2, g1.CompareTo(g2), g1.CompareTo((Object)g2));
        Show("Double:   ", h1, h2, h1.CompareTo(h2), h1.CompareTo((Object)h2));
        Show("Char:     ", i1, i2, i1.CompareTo(i2), i1.CompareTo((Object)i2));
        Show("String:   ", j1, j2, j1.CompareTo(j2), j1.CompareTo((Object)j2));
        Show("DateTime: ", k1, k2, k1.CompareTo(k2), k1.CompareTo((Object)k2));
        Show("TimeSpan: ", l1, l2, l1.CompareTo(l2), l1.CompareTo((Object)l2));
        Show("Version:  ", m1, m2, m1.CompareTo(m2), m1.CompareTo((Object)m2));
        Show("Guid:     ", n1, n2, n1.CompareTo(n2), n1.CompareTo((Object)n2));
//
        Console.WriteLine("{0}The following types are not CLS-compliant:", nl);
        Show("SByte:    ", w1, w2, w1.CompareTo(w2), w1.CompareTo((Object)w2));
        Show("UInt16:   ", x1, x2, x1.CompareTo(x2), x1.CompareTo((Object)x2));
        Show("UInt32:   ", y1, y2, y1.CompareTo(y2), y1.CompareTo((Object)y2));
        Show("UInt64:   ", z1, z2, z1.CompareTo(z2), z1.CompareTo((Object)z2));
        }
    catch (Exception e)
        {
        Console.WriteLine(e);
        }
    }

    public static void Show(string caption, Object var1, Object var2, 
                            int resultGeneric, int resultNonGeneric)
    {
    string relation;

    Console.Write(caption);
    if (resultGeneric == resultNonGeneric) 
        {
        if      (resultGeneric < 0) relation = "less than";
        else if (resultGeneric > 0) relation = "greater than";
        else                        relation = "equal to";
        Console.WriteLine("{0} is {1} {2}", var1, relation, var2);
        }

// The following condition will never occur because the generic and non-generic
// CompareTo methods are equivalent.

    else
        {
        Console.WriteLine("Generic CompareTo = {0}; non-generic CompareTo = {1}", 
                           resultGeneric, resultNonGeneric);
        }
   }
}
/*
This example produces the following results:

The following is the result of using the generic and non-generic versions of the
CompareTo method for several base types:

Boolean:  True is equal to True
Byte:     1 is equal to 1
Int16:    -2 is less than 2
Int32:    3 is equal to 3
Int64:    4 is greater than -4
Decimal:  -5.5 is less than 5.5
Single:   6.6 is equal to 6.6
Double:   7.7 is greater than -7.7
Char:     A is equal to A
String:   abc is equal to abc
DateTime: 12/1/2003 5:37:46 PM is equal to 12/1/2003 5:37:46 PM
TimeSpan: 11.22:33:44 is equal to 11.22:33:44
Version:  1.2.333.4 is less than 2.0
Guid:     ca761232-ed42-11ce-bacd-00aa0057b223 is equal to ca761232-ed42-11ce-bacd-00
aa0057b223

The following types are not CLS-compliant:
SByte:    8 is equal to 8
UInt16:   9 is equal to 9
UInt32:   10 is equal to 10
UInt64:   11 is equal to 11
*/
' This example demonstrates the generic and non-generic versions of the 
' CompareTo method for several base types.
' The non-generic version takes a parameter of type Object, while the generic
' version takes a type-specific parameter, such as Boolean, Int32, or Double.

Class Sample
   Public Shared Sub Main()
      Dim nl As String = Environment.NewLine
      Dim msg As String = _
          "{0}The following is the result of using the generic and non-generic{0}" & _
          "versions of the CompareTo method for several base types:{0}"
      
      Dim now As DateTime = DateTime.Now
      ' Time span = 11 days, 22 hours, 33 minutes, 44 seconds
      Dim tsX As New TimeSpan(11, 22, 33, 44)
      ' Version = 1.2.333.4
      Dim versX As New Version("1.2.333.4")
      ' Guid = CA761232-ED42-11CE-BACD-00AA0057B223
      Dim guidX As New Guid("{CA761232-ED42-11CE-BACD-00AA0057B223}")
      
      Dim a1 As [Boolean] = True,    a2 As [Boolean] = True
      Dim b1 As [Byte] = 1,          b2 As [Byte] = 1
      Dim c1 As Int16 = -2,          c2 As Int16 = 2
      Dim d1 As Int32 = 3,           d2 As Int32 = 3
      Dim e1 As Int64 = 4,           e2 As Int64 = -4
      Dim f1 As [Decimal] = -5.5D,   f2 As [Decimal] = 5.5D
      Dim g1 As [Single] = 6.6F,     g2 As [Single] = 6.6F
      Dim h1 As [Double] = 7.7,      h2 As [Double] = -7.7
      Dim i1 As [Char] = "A"c,       i2 As [Char] = "A"c
      Dim j1 As String = "abc",      j2 As String = "abc"
      Dim k1 As DateTime = now,      k2 As DateTime = now
      Dim l1 As TimeSpan = tsX,      l2 As TimeSpan = tsX
      Dim m1 As Version = versX,     m2 As New Version("2.0")
      Dim n1 As Guid = guidX,        n2 As Guid = guidX
      
      ' The following types are not CLS-compliant.
      ' SByte, UInt16, UInt32, UInt64

      Console.WriteLine(msg, nl)
      Try
         ' The second and third Show method call parameters are automatically boxed because
         ' the second and third Show method declaration arguments expect type Object.

         Show("Boolean:  ", a1, a2, a1.CompareTo(a2), a1.CompareTo(CObj(a2)))
         Show("Byte:     ", b1, b2, b1.CompareTo(b2), b1.CompareTo(CObj(b2)))
         Show("Int16:    ", c1, c2, c1.CompareTo(c2), c1.CompareTo(CObj(c2)))
         Show("Int32:    ", d1, d2, d1.CompareTo(d2), d1.CompareTo(CObj(d2)))
         Show("Int64:    ", e1, e2, e1.CompareTo(e2), e1.CompareTo(CObj(e2)))
         Show("Decimal:  ", f1, f2, f1.CompareTo(f2), f1.CompareTo(CObj(f2)))
         Show("Single:   ", g1, g2, g1.CompareTo(g2), g1.CompareTo(CObj(g2)))
         Show("Double:   ", h1, h2, h1.CompareTo(h2), h1.CompareTo(CObj(h2)))
         Show("Char:     ", i1, i2, i1.CompareTo(i2), i1.CompareTo(CObj(i2)))
         Show("String:   ", j1, j2, j1.CompareTo(j2), j1.CompareTo(CObj(j2)))
         Show("DateTime: ", k1, k2, k1.CompareTo(k2), k1.CompareTo(CObj(k2)))
         Show("TimeSpan: ", l1, l2, l1.CompareTo(l2), l1.CompareTo(CObj(l2)))
         Show("Version:  ", m1, m2, m1.CompareTo(m2), m1.CompareTo(CObj(m2)))
         Show("Guid:     ", n1, n2, n1.CompareTo(n2), n1.CompareTo(CObj(n2)))
         '
         Console.WriteLine("{0}The following types are not CLS-compliant:", nl)
         Console.WriteLine("SByte, UInt16, UInt32, UInt64")

      Catch e As Exception
         Console.WriteLine(e)
      End Try
   End Sub
   
   Public Shared Sub Show(caption As String, var1 As [Object], var2 As [Object], _
                          resultGeneric As Integer, resultNonGeneric As Integer)
      Dim relation As String
      
      Console.Write(caption)
      If resultGeneric = resultNonGeneric Then
         If resultGeneric < 0 Then
            relation = "less than"
         ElseIf resultGeneric > 0 Then
            relation = "greater than"
         Else
            relation = "equal to"
         End If
         Console.WriteLine("{0} is {1} {2}", var1, relation, var2)
      
      ' The following condition will never occur because the generic and non-generic
      ' CompareTo methods are equivalent.

      Else
         Console.WriteLine("Generic CompareTo = {0}; non-generic CompareTo = {1}", _
                            resultGeneric, resultNonGeneric)
      End If
   End Sub
End Class
'
'This example produces the following results:
'
'The following is the result of using the generic and non-generic versions of the
'CompareTo method for several base types:
'
'Boolean:  True is equal to True
'Byte:     1 is equal to 1
'Int16:    -2 is less than 2
'Int32:    3 is equal to 3
'Int64:    4 is greater than -4
'Decimal:  -5.5 is less than 5.5
'Single:   6.6 is equal to 6.6
'Double:   7.7 is greater than -7.7
'Char:     A is equal to A
'String:   abc is equal to abc
'DateTime: 12/1/2003 5:37:46 PM is equal to 12/1/2003 5:37:46 PM
'TimeSpan: 11.22:33:44 is equal to 11.22:33:44
'Version:  1.2.333.4 is less than 2.0
'Guid:     ca761232-ed42-11ce-bacd-00aa0057b223 is equal to ca761232-ed42-11ce-bacd-00
'aa0057b223
'
'The following types are not CLS-compliant:
'SByte, UInt16, UInt32, UInt64
'

備註

值必須完全相同,才能視為相等。Values must be identical to be considered equal. 浮點值通常會失去精確度,而且幾乎完全相同,除非它們的最小有效位數,特別是當值相依于多個數學運算時。It is common for floating-point values to lose precision and to become nearly identical except for their least significant digits, especially when the values depend on multiple mathematical operations. 因此,CompareTo 方法的傳回值有時可能會感到驚訝。Because of this, the return value of the CompareTo method at times may seem surprising. 例如,以任何值乘以後面接著相同值的除法,應該會產生原始值。For example, multiplication by any value followed by division by the same value should produce the original value. 不過,在下列範例中,計算值會變成大於原始值。However, in the following example, the computed value turns out to be greater than the original value. 使用 "R"標準數值格式字串來顯示這兩個值的所有有效位數,表示計算值與其最小有效位數中的原始值不同。Showing all significant digits of the two values by using the "R" standard numeric format string indicates that the computed value differs from the original value in its least significant digits. 如需處理這類比較的相關資訊,請參閱 Equals(Single) 方法的「備註」一節。For information about handling such comparisons, see the Remarks section of the Equals(Single) method.

using System;

public class Example
{
   public static void Main()
   {
       float value1 = 16.5457f;
       float operand = 3.8899982f;
       float value2 = value1 * operand / operand;
       Console.WriteLine("Comparing {0} and {1}: {2}\n",
                         value1, value2, value1.CompareTo(value2));
       Console.WriteLine("Comparing {0:R} and {1:R}: {2}",
                         value1, value2, value1.CompareTo(value2));
   }
}
// The example displays the following output:
//       Comparing 16.5457 and 16.5457: -1
//       
//       Comparing 16.5457 and 16.545702: -1
Module Example
   Public Sub Main()
       Dim value1 As Single = 16.5457
       Dim value2 As Single = value1 * CSng(3.8899982) / CSng(3.8899982)
       Console.WriteLine("Comparing {0} and {1}: {2}",
                         value1, value2, value1.CompareTo(value2))
       Console.WriteLine()
       Console.WriteLine("Comparing {0:R} and {1:R}: {2}",
                         value1, value2, value1.CompareTo(value2))
   End Sub
End Module
' The example displays the following output:
'       Comparing 16.5457 and 16.5457: -1
'       
'       Comparing 16.5457 and 16.545702: -1

這個方法會實作用 System.IComparable<T> 介面,而且執行效果稍微優於 Single.CompareTo 方法,因為它不需要將 value 參數轉換成物件。This method implements the System.IComparable<T> interface and performs slightly better than the Single.CompareTo method because it does not have to convert the value parameter to an object.

請注意,雖然值為 NaN 的物件不會被視為等於另一個物件,其值為 NaN (甚至是其本身),但 IComparable<T> 介面要求 A.CompareTo(A) 傳回零。Note that, although an object whose value is NaN is not considered equal to another object whose value is NaN (even itself), the IComparable<T> interface requires that A.CompareTo(A) return zero.

擴展轉換Widening Conversions

視您的程式設計語言而定,可能會將 CompareTo 方法編碼,其中參數類型的位較少(較窄),而不是實例類型。Depending on your programming language, it might be possible to code a CompareTo method where the parameter type has fewer bits (is narrower) than the instance type. 這是可行的,因為有些程式設計語言會執行隱含的擴輾轉換,將參數表示為具有與實例多個位的類型。This is possible because some programming languages perform an implicit widening conversion that represents the parameter as a type with as many bits as the instance.

例如,假設實例類型為 Single,且參數類型為 Int32For example, suppose the instance type is Single and the parameter type is Int32. Microsoft C#編譯器會產生指示,以 Single 物件的形式來表示參數的值,然後產生 Single.CompareTo(Single) 方法來比較實例的值和參數的加寬標記法。The Microsoft C# compiler generates instructions to represent the value of the parameter as a Single object, then generates a Single.CompareTo(Single) method that compares the values of the instance and the widened representation of the parameter.

請參閱程式設計語言的檔,以判斷其編譯器是否執行數數值型別的隱含擴輾轉換。Consult your programming language's documentation to determine if its compiler performs implicit widening conversions of numeric types. 如需詳細資訊,請參閱類型轉換表主題。For more information, see the Type Conversion Tables topic.

比較的有效位數Precision in Comparisons

超出記載精確度的浮點數精確度,是 .NET Framework 的實值和版本所特有。The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework. 因此,兩個特定數位的比較可能會在 .NET Framework 版本之間變更,因為數位的內部標記法的精確度可能會改變。Consequently, a comparison of two particular numbers might change between versions of the .NET Framework because the precision of the numbers' internal representation might change.

另請參閱

適用於