谁能告诉我为什么此代码的行为方式如此?查看代码中嵌入的注释...
我是否在这里遗漏了一些明显的东西?
using System;
namespace ConsoleApplication3
{
public class Program
{
static void Main(string[] args)
{
var c = new MyChild();
c.X();
Console.ReadLine();
}
}
public class MyParent
{
public virtual void X()
{
Console.WriteLine("Executing MyParent");
}
}
delegate void MyDelegate();
public class MyChild : MyParent
{
public override void X()
{
Console.WriteLine("Executing MyChild");
MyDelegate md = base.X;
// The following two calls look like they should behave the same,
// but they behave differently!
// Why does Invoke() call the base class as expected here...
md.Invoke();
// ... and yet BeginInvoke() performs a recursive call within
// this child class and not call the base class?
md.BeginInvoke(CallBack, null);
}
public void CallBack(IAsyncResult iAsyncResult)
{
return;
}
}
}
最佳答案
我还没有答案,但是我相信我可以做一个稍微清晰一些的程序来证明这种怪异:
using System;
delegate void MyDelegate();
public class Program
{
static void Main(string[] args)
{
var c = new MyChild();
c.DisplayOddity();
Console.ReadLine();
}
}
public class MyParent
{
public virtual void X()
{
Console.WriteLine("Executing MyParent.X");
}
}
public class MyChild : MyParent
{
public void DisplayOddity()
{
MyDelegate md = base.X;
Console.WriteLine("Calling Invoke()");
md.Invoke(); // Executes base method... fair enough
Console.WriteLine("Calling BeginInvoke()");
md.BeginInvoke(null, null); // Executes overridden method!
}
public override void X()
{
Console.WriteLine("Executing MyChild.X");
}
}
这不涉及任何递归调用。结果仍然是相同的奇数:
Calling Invoke()
Executing MyParent.X
Calling BeginInvoke()
Executing MyChild.X
(如果您同意这是一个简单的复制程序,请随时替换原始问题中的代码,然后从答案中删除它:)
老实说,这对我来说似乎是个bug。我会再挖一点。
关于delegates - 通过委托(delegate)执行可重写方法时,Invoke()和BeginInvoke()的行为有所不同,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/229508/