c# - 从 List<> 获取特定项目

Question

我有问题!我发现很多人遇到同样的问题，但没有一个答案对我有帮助。我试图从 List<> 中获取特定项目，但我的“测试”结果返回 null，为什么？

public MainWindow()
{
    InitializeComponent();

    var modelList = new Model2();
    modelList.MyPropertyList.Add(new Model1 { Name = "Hej1", MyProperty1 = true });

    modelList.MyPropertyList.Add(new Model1 { Name = "Hej2", MyProperty1 = false });

    var test = modelList.MyPropertyList.Find(x => x.Name == "Hej1").MyProperty1;
}

Answer 1

根据OP评论

how do you know it is null? – dotctor 1 hour ago
When i debug the value is null.. – Dennis Eriksson 1 hour ago

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are you sure you check the value after executing the line? try adding `MessageBox.Show(test.ToString());) and see what is the result – dotctor 1 hour ago

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I feel a shame of my question.. It was working the whole time! It was my fault that i read the value before it was declared to "test"! But thanks!! – Dennis Eriksson 1 hour ago

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我认为问题是您调试程序的方式。您在行 var test = modelList.MyPropertyList.Find(x => x.Name == "Hej1").MyProperty1; 上放置了一个断点，并且执行在该行之前停止 但是你认为这一行已经执行了并且 Visual Studio 在 Autos 窗口中将 test 的值显示为 null 这让你认为 test 真的是空的。如果您通过按 F10 继续执行 或添加一行 MessageBox.Show(test.ToString()); 只是为了使上一行执行或以某种方式显示 test 的值，您会发现它不是 null。