Object.ReferenceEquals(Object, Object) 方法

参考

定义

命名空间:: System

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

确定指定的 Object 实例是否是相同的实例。

public:
 static bool ReferenceEquals(System::Object ^ objA, System::Object ^ objB);

public static bool ReferenceEquals (object objA, object objB);

public static bool ReferenceEquals (object? objA, object? objB);

static member ReferenceEquals : obj * obj -> bool

Public Shared Function ReferenceEquals (objA As Object, objB As Object) As Boolean

参数

objA: Object

要比较的第一个对象。

objB: Object

要比较的第二个对象。

Boolean

如果 objA 是与 objB 相同的实例，或如果两者均为 null，则为 true，否则为 false。

示例

以下示例用于 ReferenceEquals 确定两个对象是否为同一实例。

using namespace System;
int main()
{
   Object^ o = nullptr;
   Object^ p = nullptr;
   Object^ q = gcnew Object;
   Console::WriteLine( Object::ReferenceEquals( o, p ) );
   p = q;
   Console::WriteLine( Object::ReferenceEquals( p, q ) );
   Console::WriteLine( Object::ReferenceEquals( o, p ) );
}

/*

This code produces the following output.

True
True
False

*/

object o = null;
object p = null;
object q = new Object();

Console.WriteLine(Object.ReferenceEquals(o, p));
p = q;
Console.WriteLine(Object.ReferenceEquals(p, q));
Console.WriteLine(Object.ReferenceEquals(o, p));

// This code produces the following output:
//   True
//   True
//   False

let o: obj = null
let mutable p: obj = null
let q = obj ()

printfn $"{Object.ReferenceEquals(o, p)}"
p <- q
printfn $"{Object.ReferenceEquals(p, q)}"
printfn $"{Object.ReferenceEquals(o, p)}"

// This code produces the following output:
//   True
//   True
//   False

Public Class App
    Public Shared Sub Main() 
        Dim o As Object = Nothing
        Dim p As Object = Nothing
        Dim q As New Object
        Console.WriteLine(Object.ReferenceEquals(o, p))
        p = q
        Console.WriteLine(Object.ReferenceEquals(p, q))
        Console.WriteLine(Object.ReferenceEquals(o, p))
    End Sub 
End Class 
' This code produces the following output:
'
' True
' True
' False
'

注解

Equals与方法和相等运算符不同，ReferenceEquals无法重写该方法。因此，如果要测试两个对象引用是否相等，并且不确定该方法的 Equals 实现，则可以调用该方法 ReferenceEquals 。

但是，在以下两种情况下，方法的 ReferenceEquals 返回值似乎异常：

比较值类型时。如果 objA 并且 objB 是值类型，则会在将它们传递到 ReferenceEquals 方法之前进行装箱。这意味着，如果同时objA``objB表示值类型的同一实例，ReferenceEquals该方法仍返回false，如以下示例所示。

int int1 = 3;
Console.WriteLine(Object.ReferenceEquals(int1, int1));
Console.WriteLine(int1.GetType().IsValueType);

// The example displays the following output:
//       False
//       True

let int1 = 3
printfn $"{Object.ReferenceEquals(int1, int1)}"
printfn $"{int1.GetType().IsValueType}"

// The example displays the following output:
//       False
//       True

Public Module Example
   Public Sub Main
      Dim int1 As Integer = 3
      Console.WriteLine(Object.ReferenceEquals(int1, int1))
      Console.WriteLine(int1.GetType().IsValueType)
   End Sub
End Module
' The example displays the following output:
'       False
'       True

有关装箱值类型的信息，请参阅装箱和取消装箱。

比较字符串时。如果 objA 字符串和 objB 字符串为字符串，该方法 ReferenceEquals 将 true 返回字符串是实习生的。它不对值相等性执行测试。在下面的示例中， s1 并且 s2 相等，因为它们是单个实习生字符串的两个实例。但是， s3 并且 s4 不相等，因为它们虽然具有相同的字符串值，但该字符串不是实习生。

String s1 = "String1";
String s2 = "String1";
Console.WriteLine("s1 = s2: {0}", Object.ReferenceEquals(s1, s2));
Console.WriteLine("{0} interned: {1}", s1,
                  String.IsNullOrEmpty(String.IsInterned(s1)) ? "No" : "Yes");

String suffix = "A";
String s3 = "String" + suffix;
String s4 = "String" + suffix;
Console.WriteLine("s3 = s4: {0}", Object.ReferenceEquals(s3, s4));
Console.WriteLine("{0} interned: {1}", s3,
                  String.IsNullOrEmpty(String.IsInterned(s3)) ? "No" : "Yes");

// The example displays the following output:
//       s1 = s2: True
//       String1 interned: Yes
//       s3 = s4: False
//       StringA interned: No

open System

let s1 = "String1"
let s2 = "String1"
printfn $"s1 = s2: {Object.ReferenceEquals(s1, s2)}"
printfn $"""{s1} interned: {if String.IsNullOrEmpty(String.IsInterned s1) then "No" else "Yes"}"""

let suffix = "A"
let s3 = "String" + suffix
let s4 = "String" + suffix
printfn $"s3 = s4: {Object.ReferenceEquals(s3, s4)}"
printfn $"""{s3} interned: {if String.IsNullOrEmpty(String.IsInterned s3) then "No" else "Yes"}"""

// The example displays the following output:
//       s1 = s2: True
//       String1 interned: Yes
//       s3 = s4: False
//       StringA interned: No

Module Example
   Public Sub Main()
      Dim s1 As String = "String1"
      Dim s2 As String = "String1"
      Console.WriteLine("s1 = s2: {0}", Object.ReferenceEquals(s1, s2))
      Console.WriteLine("{0} interned: {1}", s1, 
                        If(String.IsNullOrEmpty(String.IsInterned(s1)), "No", "Yes"))

      Dim suffix As String = "A"
      Dim s3 = "String" + suffix
      Dim s4 = "String" + suffix
      Console.WriteLine("s3 = s4: {0}", Object.ReferenceEquals(s3, s4))
      Console.WriteLine("{0} interned: {1}", s3, 
                        If(String.IsNullOrEmpty(String.IsInterned(s3)), "No", "Yes"))
   End Sub
End Module
' The example displays the following output:
'       s1 = s2: True
'       String1 interned: Yes
'       s3 = s4: False
'       StringA interned: No

有关字符串间的详细信息，请参阅 String.IsInterned。

适用于

另请参阅

Equals(Object)

通过

Object.ReferenceEquals(Object, Object) 方法

定义

参数

返回

示例

注解

适用于

另请参阅

其他资源