包含总是假的，因为引用不一样？

Question

I am implementing an application, in which you have to validate if some object is in a list. This happens with .contains I know, but I fill up my list with an XML file, and then the object which I check if the list contains this, is newly created so the references are not the same and .Contains will always be false.
Someone who knows to fix this problem? This is the code:

if (qfs.Contains(exa.Question.File))
{
    booleansQuestionFile[i] = true;
}

The if statement is always false.

Answer 1

As described in the documentation , Contains uses the default equality comparer. To change the default behavior, make your class implement IEquatable<T> or override Equals .

Answer 2

您应该覆盖Equals方法 ，这样您就可以定义两个对象何时相同。

Answer 3

The objects that are stored in the list should implement IEquatable. This way it does not matter that the references are different it will still compare them for equality properly.

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Here is a link to an article that shows an example. And this blog post goes into more detail.

Answer 4

You can also have such code instead, it will save you the need to change the class:

if (qfs.Exists(f => f.Question.File.Equals(exa.Question.File)))
{
    booleansQuestionFile[i] = true;
}