C＃中的Object.ReferenceEquals()方法

Object.ReferenceEquals()方法用于确定指定的Object实例是否为同一实例。此方法不能被覆盖。因此，如果用户要测试两个对象引用是否相等，并且不确定是否要执行Equals方法，则可以调用ReferenceEquals方法。

Syntax: public static bool ReferenceEquals (object ob1, object ob2);

Parameters:
ob1: It is the first object to compare.
ob2: It is the second object to compare.

Return Value: This method returns true if ob1 is the same instance as ob2 or if both are null otherwise, it returns false.

下面的程序说明了Object.ReferenceEquals()方法的用法：

范例1：

// C# program to demonstrate the
// Object.ReferenceEquals(object)
// Method
using System;
using System.Globalization;
  
class GFG {
  
    // Main Method
    public static void Main()
    {
        // Declaring and initializing value1
        object v1 = null;
  
        // Declaring and initializing value2
        object v2 = null;
  
        // using ReferenceEquals(object,
        // object) method
        bool status = Object.ReferenceEquals(v1, v2);
  
        // checking the status
        if (status)
            Console.WriteLine("null is equal to null");
        else
            Console.WriteLine("null is not equal to null");
    }
}

输出：

null is equal to null

范例2：

// C# program to demonstrate the
// Object.ReferenceEquals(Object, Object)
// Method
using System;
using System.Globalization;
  
class GFG {
  
    // Main Method
    public static void Main()
    {
  
        object p = new Object();
        object q = null;
  
        // calling get() method
        get(p, null);
  
        // assigning p to q
        q = p;
        get(p, q);
        get(q, null);
    }
  
    // defining get() method
    public static void get(object v1,
                           object v2)
    {
  
        // using ReferenceEquals(Object) method
        bool status = Object.ReferenceEquals(v1, v2);
  
        // checking the status
        if (status)
            Console.WriteLine("{0} is equal to {1}",
                                            v1, v2);
        else
            Console.WriteLine("{0} is not equal to {1}",
                                                v1, v2);
    }
}

输出：

System.Object is not equal to 
System.Object is equal to System.Object
System.Object is not equal to 

注意：此处，将永远不会在输出中输出null 。

重要事项：

• 如果ob1和ob2都代表值类型的相同实例，则此方法仍然返回false。
• 如果ob1和ob2是字符串，则在字符串为Interned的情况下此方法将返回true ，因为此方法将永远不会执行值相等性的测试。

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.object.referenceequals?view=netcore-2.1