String.CompareTo 方法

定义

将此实例与指定对象或 String 进行比较,并返回一个整数,该整数指示此实例在排序顺序中是位于指定对象或 String 之前、之后还是与其出现在同一位置。

重载

CompareTo(Object)

将此实例与指定的 Object 进行比较,并指示此实例在排序顺序中是位于指定的 Object 之前、之后还是与其出现在同一位置。

CompareTo(String)

将此实例与指定的 String 对象进行比较,并指示此实例在排序顺序中是位于指定的字符串之前、之后还是与其出现在同一位置。

注解

方法的两个 CompareTo 重载执行区分区域性和区分大小写的比较。 不能使用此方法执行不区分区域性或序号比较。 为清楚起见,建议避免 CompareTo 使用 方法,改为调用 Compare 方法。

CompareTo(Object)

Source:
String.Comparison.cs
Source:
String.Comparison.cs
Source:
String.Comparison.cs

将此实例与指定的 Object 进行比较,并指示此实例在排序顺序中是位于指定的 Object 之前、之后还是与其出现在同一位置。

public int CompareTo (object? value);
public int CompareTo (object value);

参数

value
Object

一个对象,其计算结果为 String

返回

一个 32 位带符号整数,该整数指示此实例在排序顺序中是位于 value 参数之前、之后还是与其出现在同一位置。

“值” 条件
小于零 此实例位于 value 之前。
此实例在排序顺序中的位置与 value 相同。
大于零 此实例位于 value 之后。

valuenull

实现

例外

value 不是 String

示例

以下示例将 CompareTo 方法与 一起使用 Object。 由于该方法尝试将实例与 TestClass 对象进行比较String,因此 该方法会ArgumentException引发 。

using System;

public class TestClass
{}

public class Example
{
   public static void Main()
   {
      var test = new TestClass();
      Object[] objectsToCompare = { test, test.ToString(), 123,
                                    123.ToString(), "some text",
                                    "Some Text" };
      string s = "some text";
      foreach (var objectToCompare in objectsToCompare) {
         try {
            int i = s.CompareTo(objectToCompare);
            Console.WriteLine("Comparing '{0}' with '{1}': {2}",
                              s, objectToCompare, i);
         }
         catch (ArgumentException) {
            Console.WriteLine("Bad argument: {0} (type {1})",
                              objectToCompare,
                              objectToCompare.GetType().Name);
         }
      }
   }
}
// The example displays the following output:
//    Bad argument: TestClass (type TestClass)
//    Comparing 'some text' with 'TestClass': -1
//    Bad argument: 123 (type Int32)
//    Comparing 'some text' with '123': 1
//    Comparing 'some text' with 'some text': 0
//    Comparing 'some text' with 'Some Text': -1

注解

value 必须是 String 对象。

注意

方法 CompareTo 主要用于排序或按字母顺序排列操作。 当方法调用的主要目的是确定两个字符串是否等效时,不应使用它。 若要确定两个字符串是否等效,请调用 Equals 方法。

此方法使用当前区域性执行单词 (区分大小写和区分区域性的) 比较。 有关单词、字符串和序号排序的详细信息,请参阅 System.Globalization.CompareOptions

有关此方法的行为的详细信息,请参阅 方法的 String.Compare(String, String) “备注”部分。

调用方说明

字符集包括可忽略字符。 方法 CompareTo(Object) 在执行区分区域性的比较时不考虑此类字符。 例如,如果以下代码在 .NET Framework 4 或更高版本上运行,则使用软连字符或 U+00AD) 比较“animal”与“ani-mal” (比较指示这两个字符串是等效的。

using System;

public class Example
{
   public static void Main()
   {
      string s1 = "ani\u00ADmal";
      object o1 = "animal";
      
      Console.WriteLine("Comparison of '{0}' and '{1}': {2}", 
                        s1, o1, s1.CompareTo(o1));
   }
}
// The example displays the following output:
//       Comparison of 'ani-mal' and 'animal': 0

若要识别字符串比较中的可忽略字符,请调用 CompareOrdinal(String, String) 方法。

另请参阅

适用于

.NET 9 和其他版本
产品 版本
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

CompareTo(String)

Source:
String.Comparison.cs
Source:
String.Comparison.cs
Source:
String.Comparison.cs

将此实例与指定的 String 对象进行比较,并指示此实例在排序顺序中是位于指定的字符串之前、之后还是与其出现在同一位置。

public int CompareTo (string strB);
public int CompareTo (string? strB);

参数

strB
String

要与此实例进行比较的字符串。

返回

一个 32 位带符号整数,该整数指示此实例在排序顺序中是位于 strB 参数之前、之后还是与其出现在同一位置。

“值” 条件
小于零 此实例位于 strB 之前。
此实例在排序顺序中的位置与 strB 相同。
大于零 此实例位于 strB 之后。

strBnull

实现

示例

以下示例使用 CompareTo 方法将当前字符串实例与另一个字符串进行比较。

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 precedes the second in the sort order.
//       The first string follows the second in the sort order.
//       The first string follows the second in the sort order.
//       The first string precedes the second in the sort order.

以下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。

// 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
*/

注解

此方法使用当前区域性执行单词 (区分大小写和区分区域性的) 比较。 有关单词、字符串和序号排序的详细信息,请参阅 System.Globalization.CompareOptions

注意

方法 CompareTo 主要用于排序或按字母顺序排列操作。 当方法调用的主要目的是确定两个字符串是否等效时,不应使用它。 若要确定两个字符串是否等效,请调用 Equals 方法。

有关此方法的行为的详细信息,请参阅 方法的 Compare(String, String) “备注”部分。

此方法实现 System.IComparable<T> 接口,其性能略高于 String.CompareTo(Object) 方法,因为它不必确定参数是否 strB 是必须装箱的可变值类型,并且不必将其参数从 ObjectString转换为 。

调用方说明

字符集包括可忽略字符。 方法 CompareTo(String) 在执行区分区域性的比较时不考虑此类字符。 例如,如果以下代码在 .NET Framework 4 或更高版本上运行,则使用软连字符或 U+00AD) 比较“animal”与“ani-mal” (比较指示这两个字符串是等效的。

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

若要识别字符串比较中的可忽略字符,请调用 CompareOrdinal(String, String) 方法。

另请参阅

适用于

.NET 9 和其他版本
产品 版本
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0