vb.net - VB.net 中事件的显式添加/删除

Question

在 C# 中，您可以在订阅/取消订阅事件时定义显式添加/删除代码。

这在 VB.net 中可能吗？

Answer 1

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