Question

Private Sub Receiving(ByVal iAr As IAsyncResult)
    Dim nChar As Integer
    Dim newStr As String
    Try
        SyncLock client.GetStream
            Try
                nChar = client.GetStream.EndRead(iAr)
            Catch
                Console.WriteLine("exciting")
                Exit Sub
            End Try
        End SyncLock
    Catch ex As Exception
        Console.WriteLine("exciting")
        Exit Sub
    End Try

    newStr = Encoding.ASCII.GetString(bByte, 0, nChar)

    TextBox3.Text = newStr

    client.GetStream.BeginRead(bByte, 0, 4096, AddressOf Receiving, Nothing)
End Sub

我有这个代码，我正在尝试在文本框中写3我知道我需要使用委托，因为文本框在主线程中并且回调运行在单独的一个但是我如何创建我，我真的很困惑。我知道如何为一个简单的线程做到这一点，但因为这是我第一次使用异步回调，我不知道怎么做才能得到一些帮助

Answer 1

您可以通过MSDN Thread-Safe call

对该解决方案进行检查

首先需要创建一个方法来访问文本框，如下所示：

Private Sub SetText(ByVal [text] As String)

 ' InvokeRequired required compares the thread ID of the
 ' calling thread to the thread ID of the creating thread.
 ' If these threads are different, it returns true.
 If Me.textBox3.InvokeRequired Then
     Dim d As New SetTextCallback(AddressOf SetText)
     Me.Invoke(d, New Object() {[text]})
 Else
     Me.textBox3.Text = [text]
 End If
End Sub

然后你用你的线程方法调用它：

Private Sub Receiving(ByVal iAr As IAsyncResult)
Dim nChar As Integer
Dim newStr As String
Try
    SyncLock client.GetStream
        Try
            nChar = client.GetStream.EndRead(iAr)
        Catch
            Console.WriteLine("exciting")
            Exit Sub
        End Try
    End SyncLock
Catch ex As Exception
    Console.WriteLine("exciting")
    Exit Sub
End Try

newStr = Encoding.ASCII.GetString(bByte, 0, nChar)

SetText(newStr) ' Here you make the call

client.GetStream.BeginRead(bByte, 0, 4096, AddressOf Receiving, Nothing)
End Sub

希望这有帮助！

从异步回调委托

1 个答案: