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Accepted
Tim Makins
Asked: 2023-10-06 19:50:32 +0800 CST

从 C# 转换为 Vb.Net 后如何为委托错误添加 RaiseEvent

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我是 Delegates 的新手，正在尝试将以下 C# 代码转换为 Vb.Net。

原始C#代码：

    public delegate void delConnectionStatusChanged(EventDrivenTCPClient sender, ConnectionStatus status);
    public event delConnectionStatusChanged ConnectionStatusChanged;
    private ConnectionStatus _ConStat;

    public ConnectionStatus ConnectionState
    {
        get
        {
            return _ConStat;
        }
        private set
        {
            bool raiseEvent = value != _ConStat;
            _ConStat = value;
            if (ConnectionStatusChanged != null && raiseEvent)
                ConnectionStatusChanged.BeginInvoke(this, _ConStat, new AsyncCallback(cbChangeConnectionStateComplete), this);
        }
    }


    private void cbChangeConnectionStateComplete(IAsyncResult result)
    {
        var r = result.AsyncState as EventDrivenTCPClient;
        if (r == null)
            throw new InvalidOperationException("Invalid IAsyncResult - Could not interpret as a EDTC object");
        r.ConnectionStatusChanged.EndInvoke(result);
    }

转换为Vb.Net代码：

    Public Delegate Sub delConnectionStatusChanged(ByVal sender As EventDrivenTCPClient, ByVal status As ConnectionStatus)
    Public Event ConnectionStatusChanged As delConnectionStatusChanged
    Private _ConStat As ConnectionStatus

    Public Property ConnectionState As ConnectionStatus
        Get
            Return _ConStat
        End Get
        Private Set(ByVal value As ConnectionStatus)
            Dim [raiseEvent] As Boolean = value <> _ConStat
            _ConStat = value
            If ConnectionStatusChanged IsNot Nothing AndAlso [raiseEvent] Then ConnectionStatusChanged.BeginInvoke(Me, _ConStat, New AsyncCallback(AddressOf cbChangeConnectionStateComplete), Me)
        End Set
    End Property


    Private Sub cbChangeConnectionStateComplete(ByVal result As IAsyncResult)
        Dim r = TryCast(result.AsyncState, EventDrivenTCPClient)
        If r Is Nothing Then Throw New InvalidOperationException("Invalid IAsyncResult - Could not interpret as a EDTC object")
        r.ConnectionStatusChanged.EndInvoke(result)
    End Sub

完整的源代码和转换可以在以下位置查看： https: //pastebin.com/LuvqDvtM

转换后，我收到相同的行错误：

    r.ConnectionStatusChanged.EndInvoke(result)

和

    ConnectionStatusChanged.BeginInvoke(Me, _ConStat, New AsyncCallback(AddressOf cbChangeConnectionStateComplete), Me)

错误 BC32022“公共事件 ConnectionStatusChanged As EventDrivenTCPClient.delConnectionStatusChanged”是一个事件，无法直接调用。使用“RaiseEvent”语句引发事件。

因此，我了解到该行是一个事件，我可以使用“RaiseEvent”语句来代替，但我不明白该行实际上在做什么，或者“RaiseEvent”的处理程序应该是什么。

vb.net

1 个回答

  1. Best Answer

    C# 事件被视为常规委托，可以被 Invoked 和 BeginInvoked（异步调用处理程序），而 VB.Net 似乎并不容易做到这一点。您可以创建您自己的该委托版本，它不是事件，因此您可以对其进行 BeginInvoke。

    Public Event ConnectionStatusChanged As delConnectionStatusChanged
Private connectionStatusChangedDelegate As delConnectionStatusChanged

'...

Dim raise = value <> _ConStat
_ConStat = value
If raise Then
    connectionStatusChangedDelegate = New delConnectionStatusChanged(Sub(sender, status) RaiseEvent ConnectionStatusChanged(sender, status))
    connectionStatusChangedDelegate.BeginInvoke(Me, _ConStat, New AsyncCallback(AddressOf cbChangeConnectionStateComplete), Me)
End If

'...

Private Sub cbChangeConnectionStateComplete(ByVal result As IAsyncResult)
    Dim r = TryCast(result.AsyncState, EventDrivenTCPClient)
    If r Is Nothing Then Throw New InvalidOperationException("Invalid IAsyncResult - Could not interpret as a EDTC object")
    r.connectionStatusChangedDelegate.EndInvoke(result)
End Sub

    委托被异步调用，这只会引发事件。这将允许事件处理程序异步运行，并且仍然调用 EndInvoke 来等待所有处理程序（它们的调用委托）完成。

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