Single.CompareTo 方法

定义

将此实例与指定对象或其他 Single 实例进行比较,并返回一个整数,该整数指示此实例的值是小于、等于还是大于指定对象或其他 Single 实例的值。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.

重载

CompareTo(Object)

将此实例与指定对象进行比较,并返回一个整数,该整数指示此实例的值是小于、等于还是大于指定对象的值。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)

将此实例与指定的单精度浮点数进行比较,并返回一个整数,该整数指示此实例的值是小于、等于还是大于指定单精度浮点数的值。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)

将此实例与指定对象进行比较,并返回一个整数,该整数指示此实例的值是小于、等于还是大于指定对象的值。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

参数

value
Object

要比较的对象,或为 nullAn object to compare, or null.

返回

一个带符号数字,指示此实例和 value 的相对值。A signed number indicating the relative values of this instance and value.

返回值Return Value 说明Description
小于零Less than zero 此实例小于 valueThis instance is less than value. -or- 此实例不是数字 (NaN) 而 value 是数字。This instance is not a number (NaN) and value is a number.
Zero 此实例等于 valueThis instance is equal to value. -or- 此实例和值都不是数字 (NaN)、PositiveInfinityNegativeInfinityThis instance and value are both not a number (NaN), PositiveInfinity, or NegativeInfinity.
大于零Greater than zero 此实例大于 valueThis instance is greater than value. -or- 此实例是数字而 value 不是数字 (NaN)。This instance is a number and value is not a number (NaN). -or- valuenullvalue is null.

实现

异常

value 不是 Singlevalue is not a Single.

示例

下面的代码示例演示 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

注解

value 参数必须 nullSingle的实例;否则,将引发异常。The value parameter must be null or an instance of Single; otherwise, an exception is thrown. 无论其值如何,Single的任何实例都视为大于 nullAny instance of Single, regardless of its value, is considered greater than null.

值必须完全相同,才能视为相等。Values must be identical to be considered equal. 特别是当浮点值依赖于多个数学运算时,通常情况下,它们会丢失精度,并且它们的值几乎完全相同,只是它们的最小有效位除外。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 方法的返回值可能会很奇怪。Because of this, the return value of the CompareTo method may seem surprising at times. 例如,按某个特定值(后跟同一个值相除)的乘法应生成原始值,但在下面的示例中,计算所得的值将变为大于原始值。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"标准数字格式字符串显示这两个值的所有有效位数,表示计算所得的值与最小有效位中的原始值不同。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. 有关处理此类比较的信息,请参阅 Equals(Single) 方法的 "备注" 部分。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

实现此方法是为了支持 IComparable 接口。This method is implemented to support the IComparable interface. 请注意,虽然 NaN 不被视为等于其他 NaN (甚至是自身),IComparable 接口要求 A.CompareTo(A) 返回零。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.

比较中的精度Precision in Comparisons

超出所记录精度的浮点数的精度特定于 .NET Framework 的实现和版本。The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework. 因此,两个特定数字的比较可能会在 .NET Framework 的不同版本之间发生变化,因为数字的内部表示形式的精度可能会改变。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.

另请参阅

CompareTo(Single)

将此实例与指定的单精度浮点数进行比较,并返回一个整数,该整数指示此实例的值是小于、等于还是大于指定单精度浮点数的值。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

参数

value
Single

要比较的单精度浮点数。A single-precision floating-point number to compare.

返回

一个带符号数字,指示此实例和 value 的相对值。A signed number indicating the relative values of this instance and value.

返回值Return Value 说明Description
小于零Less than zero 此实例小于 valueThis instance is less than value. -or- 此实例不是数字 (NaN) 而 value 是数字。This instance is not a number (NaN) and value is a number.
Zero 此实例等于 valueThis instance is equal to value. -or- 此实例和 value 都不是数字 (NaN)、PositiveInfinityNegativeInfinityBoth this instance and value are not a number (NaN), PositiveInfinity, or NegativeInfinity.
大于零Greater than zero 此实例大于 valueThis instance is greater than value. -or- 此实例是数字而 value 不是数字 (NaN)。This instance is a number and value is not a number (NaN).

实现

示例

下面的代码示例演示了多个值和引用类型的 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
'

注解

值必须完全相同,才能视为相等。Values must be identical to be considered equal. 浮点值通常会丢失精度,并且几乎完全相同,只是它们的最小有效位除外,特别是当值依赖于多个数学运算时。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 方法的返回值的时间可能看起来很奇怪。Because of this, the return value of the CompareTo method at times may seem surprising. 例如,如果将任何值乘以相同值相除的任何值,则应生成原始值。For example, multiplication by any value followed by division by the same value should produce the original value. 但是,在下面的示例中,计算所得的值为大于原始值。However, in the following example, the computed value turns out to be greater than the original value. 使用 "R"标准数字格式字符串显示这两个值的所有有效位数,表示计算所得的值与最小有效位中的原始值不同。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. 有关处理此类比较的信息,请参阅 Equals(Single) 方法的 "备注" 部分。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

此方法实现 System.IComparable<T> 接口,并比 Single.CompareTo 方法稍微好些,因为它不必将 value 参数转换为对象。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.

请注意,尽管值为 NaN 的对象不被视为等于其值为 NaN 的另一个对象(即使是自身),IComparable<T> 接口要求 A.CompareTo(A) 返回零。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.

扩大转换Widening Conversions

根据您的编程语言,可能会编写一个 CompareTo 方法,其中参数类型的位数(比实例类型小)。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. 这是可能的,因为某些编程语言会执行将参数表示为类型的隐式扩大转换,该类型的位数与实例的位数一样多。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,假设实例类型为 Single 并且参数类型为 Int32For example, suppose the instance type is Single and the parameter type is Int32. Microsoft C#编译器生成说明,以将参数的值表示为 Single 对象,然后生成一个 Single.CompareTo(Single) 方法,该方法将实例的值与参数的加宽表示形式进行比较。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.

请查阅编程语言的文档,以确定其编译器是否执行数值类型的隐式扩大转换。Consult your programming language's documentation to determine if its compiler performs implicit widening conversions of numeric types. 有关详细信息,请参阅类型转换表主题。For more information, see the Type Conversion Tables topic.

比较中的精度Precision in Comparisons

超出所记录精度的浮点数的精度特定于 .NET Framework 的实现和版本。The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework. 因此,两个特定数字的比较可能会在 .NET Framework 的不同版本之间发生变化,因为数字的内部表示形式的精度可能会改变。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.

另请参阅

适用于