vb.net - 等待单元引发事件

Question

我正在尝试编写一个等待事件发生的代码。我在这个 answer 中使用了答案Tcp 通信页面。 事件 PacketReceived 将在收到数据包时引发。

Private Sub FooBar()
    'Send some Tcp Message here`

    'Wait until a reply is received here

    'Execute some code when reply is received

End Sub

这是代码发送文件名和文件的用途。它缺少文件存在性检查

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        Dim t = New Thread(AddressOf SendFile)
        Dim f = New FileAndData
        f.FileList = SlideShowItems
        f.FileType = "tempSlideShowImage"
        t.Start(f)
    End Sub

    Private Sub SendFile(obj As Object)
        Dim fD = CType(obj, FileAndData)
        For Each item In fD.FileList.Items
            Dim fileIn As New FileStream(item, FileMode.Open)
            Const chunkSize = 10485760

            Dim messageFileNamePkt As New TcpMessagePacket(Encoding.Default.GetBytes(Path.GetFileName(item)), TcpMessagePacket.PacketHeader.Filename)
            messageFileNamePkt.Send(_etcClient.Client) 'Send file name

            Dim messageFiletype As New TcpMessagePacket(Encoding.Default.GetBytes(fD.FileType), TcpMessagePacket.PacketHeader.Filetype)
            messageFiletype.Send(_etcClient.Client) 'Send file type

            'Wait here for reply if for file existence

            While fileIn.Position < fileIn.Length
                Dim bytes(chunkSize) As Byte
                If fileIn.Length - fileIn.Position < bytes.Length Then
                    ReDim bytes(fileIn.Length - fileIn.Position - 1)
                End If
                fileIn.Read(bytes, 0, bytes.Length)

                Dim messageFilePkt As New TcpMessagePacket(bytes, TcpMessagePacket.PacketHeader.FileData)
                messageFilePkt.Send(_etcClient.Client) 'Send file chunks

            End While

            fileIn.Close()
            Dim messageFileEnd As New TcpMessagePacket(Encoding.Default.GetBytes(""), TcpMessagePacket.PacketHeader.TransferComplete)
            messageFileEnd.Send(_etcClient.Client) 'Send transfer complete

        Next
    End Sub

Public Class FileAndData
    Public FileList As ListBox
    Public FileType As String
End Class

这是回复的处理程序

    Private Sub Client_PacketReceived(sender As Object, e As ExtendedTcpClient.PacketReceivedEventArgs) Handles _etcClient.PacketReceived
    End Sub

Answer 1

使用 <a href="https://msdn.microsoft.com/en-us/library/system.threading.manualresetevent(v=vs.110).aspx" rel="noreferrer noopener nofollow">ManualResetEvent</a> .例如。

Imports System.Threading
Module Module1
    Private ReadOnly WaitEvent As New ManualResetEvent(True)
    Sub Main()
        For i = 1 To 100
            WaitEvent.WaitOne() 'This is like a door. It's open because of ManualResetEvent(True)
            If i = 50 Then
                WaitEvent.Reset() 'This closes the door
            End If
            Console.WriteLine(i)
        Next
        Console.Read()
    End Sub
    Private Sub SetTheEventWhenCalled()
        WaitEvent.Set() 'This on the other hand, Opens the door
    End Sub
End Module