CompareTo 方法 (String)
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String.CompareTo 方法 (String)

 

Compares this instance with a specified String object and indicates whether this instance precedes, follows, or appears in the same position in the sort order as the specified string.

命名空间:   System
程序集:  mscorlib(mscorlib.dll 中)

public int CompareTo(
	string strB
)

参数

strB
Type: System.String

The string to compare with this instance.

返回值

Type: System.Int32

A 32-bit signed integer that indicates whether this instance precedes, follows, or appears in the same position in the sort order as the strB parameter.

Value

Condition

Less than zero

This instance precedes strB.

Zero

This instance has the same position in the sort order as strB.

Greater than zero

This instance follows strB.

-or-

strB is null.

This method performs a word (case-sensitive and culture-sensitive) comparison using the current culture. For more information about word, string, and ordinal sorts, see T:System.Globalization.CompareOptions.

System_CAPS_caution小心

The M:System.String.CompareTo(System.Object) method was designed primarily for use in sorting or alphabetizing operations. It should not be used when the primary purpose of the method call is to determine whether two strings are equivalent. To determine whether two strings are equivalent, call the Overload:System.String.Equals method.

For more information about the behavior of this method, see the Remarks section of the M:System.String.Compare(System.String,System.String) method.

This method implements the T:System.IComparable`1 interface and performs slightly better than the M:System.String.CompareTo(System.Object) method, because it does not have to determine whether the strB argument is a mutable value type that must be boxed, and it does not have to cast its parameter from an T:System.Objectto aT:System.String.

对调用方的说明:

Character sets include ignorable characters. The M:System.String.CompareTo(System.String) method does not consider such characters when it performs a culture-sensitive comparison. For example, if the following code is run on the netfx40_short or later, a comparison of "animal" with "ani-mal" (using a soft hyphen, or U+00AD) indicates that the two strings are equivalent.

using System;

public class Example
{
   public static void Main()
   {
      string s1 = "ani\u00ADmal";
      string s2 = "animal";

      Console.WriteLine("Comparison of '{0}' and '{1}': {2}", 
                        s1, s2, s1.CompareTo(s2));
   }
}
// The example displays the following output:
//       Comparison of 'ani-mal' and 'animal': 0

To recognize ignorable characters in a string comparison, call the M:System.String.CompareOrdinal(System.String,System.String) method.

The following example uses the M:System.String.CompareTo(System.Object) method to compare the current string instance with another string.

using System;

public class Example
{
   public static void Main()
   {
      string strFirst = "Goodbye";
      string strSecond = "Hello";
      string strThird = "a small string";
      string strFourth = "goodbye";

      // Compare a string to itself.
      Console.WriteLine(CompareStrings(strFirst, strFirst));

      Console.WriteLine(CompareStrings(strFirst, strSecond));
      Console.WriteLine(CompareStrings(strFirst, strThird));

      // Compare a string to another string that varies only by case.
      Console.WriteLine(CompareStrings(strFirst, strFourth));
      Console.WriteLine(CompareStrings(strFourth, strFirst));
   }

   private static string CompareStrings( string str1, string str2 )
   {
      // Compare the values, using the CompareTo method on the first string.
      int cmpVal = str1.CompareTo(str2);

	   if (cmpVal == 0) // The strings are the same.
         return "The strings occur in the same position in the sort order.";
      else if (cmpVal > 0)
         return "The first string precedes the second in the sort order.";
      else
         return "The first string follows the second in the sort order.";
    }
}
// The example displays the following output:
//       The strings occur in the same position in the sort order.
//       The first string follows the second in the sort order.
//       The first string precedes the second in the sort order.
//       The first string precedes the second in the sort order.
//       The first string follows the second in the sort order.

The following example demonstrates generic and non-generic versions of the CompareTo method for several value and reference types.

// 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
*/

Universal Windows Platform
4.5 后可用
.NET Framework
1.1 后可用
Portable Class Library
受以下版本支持:portable .NET platforms
Silverlight
2.0 后可用
Windows Phone Silverlight
7.0 后可用
Windows Phone
8.1 后可用
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