C# TargetInitationException -（不应该存在？）

发布于 2024-12-01 10:19:21 字数 691 浏览 2 评论 0原文

我正在尝试在 WPF 中制作一个简单的应用程序，但遇到了一些异常情况。我有 2 个类：一个部分类（用于 WPF 窗口），另一个是我自己设置的公共类。当我尝试访问从 WPF 窗口类创建的类时，我遇到了 TargetInitationException ，告诉我对象引用未设置为对象的实例。但是，导致异常的对象引用被设置为对象的实例。

这是我的代码：

public partial class MainWindow : Window
{
    CurrentParent CP = new CurrentParent();
    public MainWindow()
    {
        InitializeComponent();
        CP.Par.Add("MainCanvas");
    }
}

public class CurrentParent
{
    private List<string> _Par;

    public List<string> Par
    {
        get { return _Par; }
        set { _Par = value; }
    }
}

当然，这是在一个名称空间中。我看不出为什么会出现此错误，因为我的对象引用 CP 显然是 CurrentParent 的实例。

有人知道如何解决这个问题吗？提前致谢！

-伊恩

原文

I am trying to make a simple app in WPF, and i've run into a bit of an anomaly. I have 2 classes: a partial class (for the WPF Window), and another public class I have set up myself. When I try to access the class I created from the WPF window class, I run into a TargetInvocationException telling me the object reference is not set to an instance of an object. However, the object reference that results in the exception is set to an instance of an object.

Here's my code:

public partial class MainWindow : Window
{
    CurrentParent CP = new CurrentParent();
    public MainWindow()
    {
        InitializeComponent();
        CP.Par.Add("MainCanvas");
    }
}

public class CurrentParent
{
    private List<string> _Par;

    public List<string> Par
    {
        get { return _Par; }
        set { _Par = value; }
    }
}

Of course, this is in one namespace. I cannot see any reason why I should be getting this error, as my object reference CP clearly is an instance of CurrentParent.

Would anybody have any idea of how to fix this? Thanks in advance!

-Ian

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梦冥 2024-12-08 10:19:21

在 CurrentParent 中，字段 _Par 从未初始化，因此 CP.Par 为 null。当框架尝试调用 Add 时，会引发异常。您需要初始化_Par：

public class CurrentParent
{
    private List<string> _Par = new List<string>();

    public List<string> Par
    {
        get { return _Par; }
        set { _Par = value; }
    }
}

In CurrentParent the field _Par is never initialized and therefore CP.Par is null. The exception is thrown when the frameworks tries to call Add. You need to initialze _Par:

public class CurrentParent
{
    private List<string> _Par = new List<string>();

    public List<string> Par
    {
        get { return _Par; }
        set { _Par = value; }
    }
}

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浪漫人生路 2024-12-08 10:19:21

您没有实例化 CurrentParent 类中的 _Par 成员。这应该可以解决您的问题：

public class CurrentParent
{
 public CurrentParent()
 {
  this.Par = new List<String>();
 }

 public List<String> Par { get; set; }
}

请注意，该示例使用自动属性。这是一个更详细的示例，可以更好地突出您的问题：

public class CurrentParent
{
 public CurrentParent()
 {
  this._Par = new List<String>();
 }

 public List<String> Par
 {
  get { return this._Par; }
  set { this._Par = value; }
 }

 private List<String> _Par;
}

You are not instantiating the _Par member in the CurrentParent class. This should solve your problem:

public class CurrentParent
{
 public CurrentParent()
 {
  this.Par = new List<String>();
 }

 public List<String> Par { get; set; }
}

Note that the sample uses automatic properties. Here is a more verbose sample that better highlights your problem:

public class CurrentParent
{
 public CurrentParent()
 {
  this._Par = new List<String>();
 }

 public List<String> Par
 {
  get { return this._Par; }
  set { this._Par = value; }
 }

 private List<String> _Par;
}

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