如何将此C＃事件/委托代码转换为VB.NET（2008或2010） [英] How to Convert This C# Event/Delegate Code Into VB.NET (2008 or 2010)

问题描述

从C＃到VB.NET这是相关的C＃代码

C# to VB.NET Here is the relevant C# Code

namespace MyApp {
   public delegate bool AllocHandlerDelegate(int param1);

   public interface ILoader  {
    event AllocHandlerDelegate evAlloc;
    bool Load();
    }

   public class MyLoader : ILoader  {
    public event AllocHandlerDelegate evAlloc;

        public bool Load() {
            try  {
           if (this.evAlloc != null && !evAlloc(1))
                          return false;
        }
   }
}

这就是我的想法到目前为止。
C＃委托是一个返回布尔结果的函数。因此，我将委托定义和事件声明转换如下。

Here is what I came up with so far. The C# delegate is a function which returns a boolean result. So I converted the delegate definition and event declaration as follow.

    Public Delegate Function AllocHandlerDelegate(ByVal param1 As Integer) As Boolean
    Public Event evAlloc As AllocHandlerDelegate

Visual Studio返回了错误消息：事件不能被声明为具有返回类型的委托类型。

Visual Studio Returned with the Error Message: "Events cannot be declared with a delegate type that has a return type."

因此，我将其改为SUB并完成了这种翻译*。

So I made it a SUB instead and completed the translation like this*.

Namespace MyApp
    Public Delegate Sub AllocHandlerDelegate(ByVal param1 As Integer)

    Public Interface ILoader
        Event evAlloc As AllocHandlerDelegate

    Function Load() As Boolean
    End Interface

    Public Class MyLoader
        Implements ILoader

        Public Event evAlloc As AllocHandlerDelegate Implements ILoader.evAlloc

        Public Function Load() as Boolean Implements ILoad.Load
            Try
                    If Me.evAllocEvent IsNot Nothing AndAlso Not evAlloc(1) Then
                        Return False
            End Try
        End Function
    End Class
End Namespace

*注意：我已经意识到我无法检查 Event对象什么都不是，只是对于VB内部委托对象* EVENTNAME * Event。

*Note: I already realized that I could not check for the "Event" object to be nothing, but for the VB internal Delegate Object *EVENTNAME*Event.

但是对于第二部分，我不知道该怎么做用它做。我收到以下错误消息：
公共事件evAlloc（以整数形式的param1）是一个事件，不能直接调用。使用'RaiseEvent'语句引发事件。

However for the second part I don't know what to do with it. There I get the following Error message: 'Public Event evAlloc (param1 As Integer)' is an event, and cannot be called directly. Use a 'RaiseEvent' statement to raise an event.

有什么想法吗？！谢谢

推荐答案

错误消息非常清楚：

公共事件evAlloc（作为整数的param1）是一个事件，不能直接调用。使用'RaiseEvent'语句引发事件。

Public Event evAlloc (param1 As Integer)' is an event, and cannot be called directly. Use a 'RaiseEvent' statement to raise an event.

这是一个事件，您不能直接调用它。改用'RaiseEvent'语句：

It's an event, you can't not call it directly. Use a 'RaiseEvent' statement instead:

RaiseEvent evAlloc(1)

您的事件无法返回值（C＃等效项可以返回），但是您可以使用普通委托。

Your event can't return a value (the C# equivalent can), but you can use a plain delegate instead.

Public Delegate Function AllocHandlerDelegate(ByVal param1 As Integer) As Boolean

Public Interface ILoader
    Property evAlloc As AllocHandlerDelegate
    Function Load() As Boolean
End Interface

Public Class MyLoader
    Implements ILoader

    Public Property evAlloc As AllocHandlerDelegate Implements ILoader.evAlloc

    Public Function Load() as Boolean Implements ILoader.Load
            If Me.evAlloc IsNot Nothing AndAlso Not evAlloc(1) Then _
                Return False
            ' Do Stuff '
            Return True
    End Function
End Class

使用返回值错误的事件，因为事件可能会导致多重后果订阅者人数众多，您可能不知道会返回哪个值。

Using events that return values are bad, since events can have multiple subscribers and you probably don't know which value will get returned.

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