Question

我收到此错误，无法理解此错误。我使用win form和.net 3.5。问题是，这可以编译和间歇。今天刚刚出现，所以我猜这种情况非常罕见（可能在5000次运行后一次）。我想知道是什么导致了这个错误，以及任何可能的解决方法。以下是我如何实现代码的示例。

我的应用程序是多线程的，这个方法是单例。

Exception type: System.ArgumentException
Exception message: Delegate to an instance method cannot have null 'this'.
Exception stack trace: 
   at System.MulticastDelegate.ThrowNullThisInDelegateToInstance()
   at System.MulticastDelegate.CtorClosed(Object target, IntPtr methodPtr)

  class Caller
  {
    private ClassA theA;
    public Caller()
    {
      theA = new ClassA();
    }

    public void button_click()
    {
      theA.Execute(false);
    }
    public void button2_click()
    {
      theA.Execute( true );
    }
  }

  interface IClassA
  {
    void ActionMinus();
  }
  class ClassA
  {
    public int VariableA = 0;
    public void Execute( bool wait )
    {
      ClassB instanceB = new ClassB( this );
      Thread thread = new Thread( instanceB.Action ) // error in here
      { 
        Name = "Executor",
        Priority = ThreadPriority.Highest
      };

      thread.Start();
      if( wait )
        thread.Join();
    }
    public void ActionMinus()
    {
      //someAction1
      VariableA -= 2;
      //someAction2
    }
  }

  class ClassB
  {
    private readonly ClassA instanceA;
    public ClassB( ClassA instance )
    {
      instanceA = instance;
    }
    public void Action()
    {
      //some other action3
      instanceA.VariableA += 5;
      //some other action4
      instanceA.ActionMinus();
      //some other action5
    }
  }

Answer 1

看起来它对我很有用。

您的计划的背景是什么？

我写了一个包含代码的简单空shell，但程序将在线程开始之前结束。

我必须添加一个Console.ReadKey（）方法。

screenshot

以下是我使用的完整代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace DelegateToInstance {

  class Program {
    static void Main(string[] args) {
      var obj = new Caller();
      obj.button_click();
      Console.ReadKey();
    }
  }

  class Caller
  {
    private ClassA theA;
    public Caller()
    {
      theA = new ClassA();
    }

    public void button_click()
    {
      theA.Execute(false);
    }
    public void button2_click()
    {
      theA.Execute( true );
    }
  }

  interface IClassA
  {
    void ActionMinus();
  }

  class ClassA
  {
    public int VariableA = 0;
    public void Execute( bool wait )
    {
      ClassB instanceB = new ClassB(this);
      Thread thread = new Thread( instanceB.Action ) // error in here
      { 
        Name = "Executor",
        Priority = ThreadPriority.Highest
      };

      thread.Start();
      if( wait )
        thread.Join();
    }
    public void ActionMinus()
    {
      //someAction1
      VariableA -= 2;
      //someAction2
    }
  }

  class ClassB
  {
    private readonly ClassA instanceA;
    public ClassB( ClassA instance )
    {
      instanceA = instance;
    }
    public void Action()
    {
      //some other action3
      instanceA.VariableA += 5;
      //some other action4
      instanceA.ActionMinus();
      //some other action5
    }
  }

}

我讨厌选民，所以我给了你一个upvote。

委托给实例方法在运行时

1 个答案: