从methodinfo创建委托 [英] Create a delegate from methodinfo

问题描述

我有以下情况：

I have the following Situation :

Dim myType As Type = Repeat_Tastendruck_Control.GetType
 Dim myInfo As System.Reflection.MethodInfo = myType.GetMethod("OnClick", Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)

 If myInfo IsNot Nothing Then
      Dim myDelegate As delegate_OnClick = [Delegate].CreateDelegate(GetType(delegate_OnClick), myInfo, False)
     'Repeat_Tastendruck_Control.Invoke(myDelegate, Nothing)
     myDelegate(EventArgs.Empty)
     Exit Sub
 End If

我在myType中输入Repeat_Tastendruck_Control的类型

我在myInfo中获得所需的MethodInfo

如果我现在创建一个委托调用此方法它指向一个非实例宾语。那么......我的错误在哪里？

任何指导都很有用......;）



附加信息：



OnClick-Method的定义：

I get in myType the Type of Repeat_Tastendruck_Control
I get in myInfo the the required MethodInfo
If I now create a Delegate to call this Method it points to a not instanced object. So ... where is my mistake ?
Any guidance would be usefull ... ;)

Additional Information :

the definition of the OnClick-Method :

Protected Overrides Sub OnClick(e As System.EventArgs)
    MyBase.OnClick(e)
End Sub

代表的定义：

the definition of the delegate :

Private Delegate Sub delegate_OnClick(e As EventArgs)

命令myDelegate（EventArgs） .Empty）在方法中调用权限 - 但不在Repeat_Tastendruck_Control引用的Control中。



我的尝试：



...... ............................

the command "myDelegate(EventArgs.Empty)" calls the right in method - but not in the Control which is referenced by "Repeat_Tastendruck_Control".

What I have tried:

..................................

推荐答案

创建委托时指向实例方法，您必须提供 Me 对象，该对象将在调用委托时使用。因为您还没有这样做，并且您为 throwOnBindFailure 参数指定了 False ，您的委托实例将是设置为没有。



有两种方法可以解决这个问题：



1。要创建绑定到该类的单个实例的委托，请使用 CreateDelegate 重载之一接受 firstArgument 参数：

When you create a delegate pointing to an instance method, you have to provide the "Me" object which will be used when the delegate is invoked. Because you haven't done that, and you've specified False for the throwOnBindFailure parameter, your delegate instance will be set to Nothing.

There are two ways you can solve this:

1. To create a delegate bound to a single instance of the class, use one of the CreateDelegate overloads which accept a firstArgument parameter:

Dim myDelegate As delegate_OnClick = [Delegate].CreateDelegate(
    GetType(delegate_OnClick),  ' The delegate type
    Repeat_Tastendruck_Control, ' The object instance - "Me"
    myInfo)                     ' The method info

myDelegate(EventArgs.Empty)

Delegate.CreateDelegate方法（类型，对象，MethodInfo）（系统） [ ^ ]





2。创建一个可以与多个实例一起重用的委托该类，为您的委托提供一个额外的参数来表示对象实例：

Delegate.CreateDelegate Method (Type, Object, MethodInfo) (System)[^]


2. To create a delegate which can be reused with multiple instances of the class, give your delegate an extra parameter to represent the object instance:

Private Delegate Sub delegate_OnClick(ByVal instance As YourControlType, ByVal e As EventArgs)
...
Dim myDelegate As delegate_OnClick = [Delegate].CreateDelegate(GetType(delegate_OnClick), myInfo, True)

myDelegate(Repeat_Tastendruck_Control, EventArgs.Empty)

NB：委托的第一个参数的类型必须是声明方法的类型或派生类型。如果要传递接口，则 MethodInfo 必须来自接口，而不是类。

NB: The type of the first parameter for the delegate must be the type where the method is declared, or a derived type. If you want to pass an interface, then the MethodInfo must come from the interface, not the class.

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