如果(< object> ==< int>) [英] if (<object> == <int>)

问题描述

我不明白，为什么下图中的if语句返回false. 我希望你能向我解释.

I can't understand, why the if statement in the picture below returns false. I hope you can explain it to me.

您会看到，两个变量的值和类型都相同.

You can see, that the values and the typs of both variables are the same.

推荐答案

您正在调用的==运算符是带有两个object参数的重载.这使用引用相等-值并不重要，它必须是相同的对象.

The == operator you are calling is the overload that takes two object parameters. This uses reference equality - the value isn't important, it has to be the same object.

您可以在文档中阅读:

对于字符串以外的引用类型，== 如果其两个操作数引用相同的对象，则返回true .对于字符串类型，==比较字符串的值.

For reference types other than string, == returns true if its two operands refer to the same object. For the string type, == compares the values of the strings.

虽然int是值类型，但已被装箱" (包装在object中).您正在比较两种包装整数的引用类型.

While int is a value type, it has been 'boxed' (wrapped in an object). You are comparing the two different reference types that wrap your integers.

要解决此问题，可以改用object.Equals-这将比较两个整数.

To fix this, you can use object.Equals instead - this will compare the two integers.

item.Equals(value);

或静态方法(可以处理item == null的情况):

Or the static method (which would handle the case where item == null):

object.Equals(item, value);

如果您取消对int的装箱，则可以按预期使用==的int重载:

If you unbox to int then you can use the int overload of == as you expect:

(int)item == (int)value;

同样，根据文档:

对于预定义的值类型，等于运算符(==)如果其操作数的值相等，则返回true.

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