在 VB.net 中显式添加/删除事件 [英] explicit add/remove for Event in VB.net

问题描述

在 C# 中，您可以在订阅/取消订阅 event 时定义显式的 add/remove 代码.

In C# you can define explicit add/remove code when an event is subscribed/unsubscribed.

这在 VB.net 中可行吗?

Is this possible in VB.net?

推荐答案

Imports System.Runtime.CompilerServices
...
    Private propchanged As PropertyChangedEventHandler

    Public Custom Event PropertyChanged As PropertyChangedEventHandler

        <MethodImpl(MethodImplOptions.Synchronized)> _
        AddHandler(ByVal value As PropertyChangedEventHandler)
            propchanged = DirectCast([Delegate].Combine(propchanged, value), PropertyChangedEventHandler)
        End AddHandler

        <MethodImpl(MethodImplOptions.Synchronized)> _
        RemoveHandler(ByVal value As PropertyChangedEventHandler)
            propchanged = DirectCast([Delegate].Remove(propchanged, value), PropertyChangedEventHandler)
        End RemoveHandler

        RaiseEvent(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs)
            Dim handler = propchanged
            If handler IsNot Nothing Then handler(sender, e)
        End RaiseEvent
    End Event

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