Vb.net Form.show（）没有响应

我正在写一个小的POSIT程序，它应该能够让用户使用数据库向其他计算机发送小的注释。 我有一个主窗体，我可以在其中编写消息并在线查看用户，一个应该显示消息的工作表窗体和一个sql数据库，该数据库有一个用于用户和消息的表

我的想法是将消息写入Messagestable，我的程序使用它来获取新消息并在表单中显示它们。到目前为止还不错

问题是，当我向表中添加一条新消息时，SqlDependency会触发一个事件，而我的mainForm会创建一个新的工作表，该工作表会在调用sheet.Show后冻结。主窗体继续运行，但我的工作表始终没有响应

这是我的密码： DBListener：

 Imports System.Data
    Imports System.Data.Sql
    Imports System.Data.SqlClient
    Imports System.Threading

Public Class DBListener

    Private changeCount As Integer = 0

    Private Const tableName As String = "IMSMessages"
    Private Const statusMessage As String = _
       "{0} changes have occurred."
    Private exitRequested As Boolean = False
    Private waitInProgress As Boolean = False
    Private recieverHost As String
    Private imsMain As IMSMain

    Public Sub New(main As IMSMain, recieverHost As String)
        Me.imsMain = main
        Me.recieverHost = recieverHost
        initCommand(recieverHost)
        SqlDependency.Start(connectionString)
        GetMsg(recieverHost)
    End Sub


    Private connectionString As String = "Data Source=NB_RANDY\SQLEXPRESS;Initial Catalog=eurom_test;Integrated Security=SSPI;"
    Private sqlConn As SqlConnection = New SqlConnection(connectionString)
    Private commandMesg As SqlCommand = Nothing
    Private commandUsers As SqlCommand = Nothing

    Private Sub initCommand(recieverHost As String)
        commandMesg = New SqlCommand
        commandMesg.CommandText = "SELECT MessageID,SenderHost,RecieverHost,isRead,isRecieved,Stamp from dbo.IMSMessages " &
                                       "WHERE RecieverHost=@RecieverHost" &
                                       " AND isRecieved = 0"
        commandMesg.Parameters.Add("@RecieverHost", SqlDbType.VarChar).Value = recieverHost
        commandMesg.Connection = sqlConn

        commandUsers = New SqlCommand
        commandUsers.CommandText = "Select HostName From dbo.IMSUser"
    End Sub




    Private Sub OnChangeMsg(ByVal sender As System.Object, ByVal e As System.Data.SqlClient.SqlNotificationEventArgs)
        Dim dep As SqlDependency = DirectCast(sender, SqlDependency)
        RemoveHandler dep.OnChange, AddressOf OnChangeMsg
        GetMsg(recieverHost)
    End Sub
    Private Sub OnChangeUser(ByVal sender As System.Object, ByVal e As System.Data.SqlClient.SqlNotificationEventArgs)
        Dim dep As SqlDependency = DirectCast(sender, SqlDependency)
        RemoveHandler dep.OnChange, AddressOf OnChangeUser
        GetUsers()
    End Sub

    Public Sub GetMsg(recieverHost As String)
        If Not sqlConn.State = ConnectionState.Open Then
            sqlConn.Open()

        End If

        commandMesg.Notification = Nothing
        Dim dep As SqlDependency = New SqlDependency(commandMesg)
        AddHandler dep.OnChange, New OnChangeEventHandler(AddressOf OnChangeMsg)
        Dim table As DataTable = New DataTable
        Dim adapter As SqlDataAdapter = New SqlDataAdapter(commandMesg)
        adapter.Fill(table)
        imsMain.recieveNewMessages(table)
    End Sub
    Public Sub GetUsers()
        If Not sqlConn.State = ConnectionState.Open Then
            sqlConn.Open()

        End If

        commandMesg.Notification = Nothing
        Dim dep As SqlDependency = New SqlDependency(commandUsers)
        AddHandler dep.OnChange, New OnChangeEventHandler(AddressOf OnChangeUser)
        Dim table As DataTable = New DataTable   
        imsMain.updateOnlineUserList()
    End Sub


End Class

主要形式：

 Imports System.Data.SqlClient
    Imports System.Threading

    Public Class IMSMain

    Private user As IMSUser
    Private listener As DBListener


    Private sqlConn As SqlConnection

    Public Sub New()
        InitializeComponent()
        sqlConn = New SqlConnection("Data Source=NB_RANDY\SQLEXPRESS;Initial Catalog=eurom_test;Integrated Security=SSPI;")



        Me.user = New IMSUser(My.Computer.Name)
        user.register()

        updateOnlineUserList()
        listener = New DBListener(Me, user.HostName)

    End Sub
    Private Sub onSend(sender As Object, e As EventArgs) Handles bt_send.Click
        Dim command As SqlCommand = New SqlCommand
        Dim msgText = tb_text.Text
        Dim reciever As IMSUser = lb_Online.SelectedItem
        Dim insert_string As String = "Insert INTO dbo.IMSMessages(Text,RecieverHost,SenderHost,isRead,isRecieved,Stamp) Values(@Text,@RecieverHost,@SenderHost,@isRead,@isRecieved,@Stamp)"
        Dim adapter As SqlDataAdapter = New SqlDataAdapter
        Dim table As DataTable = New DataTable()
        Try

            If Not sqlConn.State = ConnectionState.Open Then
                sqlConn.Open()

            End If
            command.Connection = sqlConn
            command.CommandText = insert_string
            adapter.SelectCommand = command
            adapter.Fill(table)
            command.CommandText = insert_string
            command.Parameters.Add("@Text", SqlDbType.VarChar).Value = msgText
            command.Parameters.Add("@RecieverHost", SqlDbType.NChar).Value = reciever.HostName
            command.Parameters.Add("@SenderHost", SqlDbType.NChar).Value = user.HostName
            command.Parameters.Add("@isRecieved", SqlDbType.Bit).Value = 0
            command.Parameters.Add("@isRead", SqlDbType.Bit).Value = 0
            command.Parameters.Add("@Stamp", SqlDbType.SmallDateTime).Value = DateTime.Now
            command.ExecuteNonQuery()
        Catch ex As Exception
            Console.WriteLine("onSend: internal database exception" + ex.Message)
        End Try
    End Sub

    Private Sub processMessageId(refMessageID As Integer)
        Dim command As SqlCommand = New SqlCommand
        Dim msgID_string As String = "SELECT * from dbo.IMSMessages " &
                                       "WHERE MessageID=@MessageID AND isRecieved = 0" &
                                       " ORDER BY Stamp"
        Dim isRecievedUpdate_string As String = "Update dbo.IMSMessages " &
                                            "SET isRecieved=1" &
                                             " WHERE MessageID=@MessageID"
        Dim adapter As SqlDataAdapter = New SqlDataAdapter
        Dim table As DataTable = New DataTable()
        Try
            If Not sqlConn.State = ConnectionState.Open Then
                sqlConn.Open()

            End If
            command = New SqlCommand
            command.CommandText = msgID_string
            command.Parameters.Add("@MessageID", SqlDbType.Int).Value = refMessageID
            command.Connection = sqlConn
            adapter.SelectCommand = command
            adapter.Fill(table)
            command = New SqlCommand
            command.Connection = sqlConn
            command.CommandText = isRecievedUpdate_string
            command.Parameters.Add("@MessageID", SqlDbType.Int).Value = refMessageID
            command.ExecuteNonQuery()

        Catch ex As Exception
            Console.WriteLine("processMessageID: internal database exception" + ex.Message)
        End Try
        Try
            Dim row As DataRow = table.Rows(0)
            Dim senderHost As String = row("SenderHost")
            Dim sender As IMSUser = New IMSUser(senderHost)
            Dim currentSheet As IMSSheet
            Dim stringText As String = row("Text")
            Dim stamp As Date = row("Stamp")
            currentSheet = New IMSSheet(sender, stringText, stamp)
            currentSheet.Show()
        Catch ex As Exception
            Console.WriteLine("processMessageID: error while showing sheet")
        End Try
    End Sub

    Public Sub recieveNewMessages(newMessageTable As DataTable)
        For Each row As DataRow In newMessageTable.Rows
            Dim id As Integer = row("MessageID")
            processMessageId(id)
        Next
    End Sub

    Public Sub updateOnlineUserList()
        lb_Online.Items.Clear()
        Dim adapter As SqlDataAdapter = New SqlDataAdapter
        Dim table As DataTable = New DataTable()
        Dim command As SqlCommand = New SqlCommand
        Dim onlineUser_string = "Select * FROM dbo.IMSUser"
        command.CommandText = onlineUser_string
        Try
            If Not sqlConn.State = ConnectionState.Open Then
                sqlConn.Open()

            End If
            command.Connection = sqlConn
            adapter.SelectCommand = command
            adapter.Fill(table)
        Catch ex As Exception
            Console.WriteLine("internal database exception" + ex.Message)
        End Try
        For Each row As DataRow In table.Rows

            Dim tmp As IMSUser = New IMSUser(row("HostName"))
            If Not user.Equals(tmp) Then
                lb_Online.Items.Add(tmp)
            End If
        Next
    End Sub

End Class

表格：

    Public Class IMSSheet
        Dim IsDraggingForm As Boolean = False
        Private MousePos As New System.Drawing.Point(0, 0)

    Public Sub New(session As IMSUser, text As String, stamp As Date)
        Ini

tializeComponent()
            Me.tb_sender.Text = session.HostName
            addText(text, stamp)
        End Sub

        Private Sub addText(msg As String, stamp As DateTime)
            Dim currentText As String = tb_text.Text
            currentText = currentText + stamp.ToString + Environment.NewLine + msg + Environment.NewLine
            tb_text.Text = currentText
        End Sub
        Private Sub IMSSheet_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseDown
            If e.Button = MouseButtons.Left Then
                IsDraggingForm = True
                MousePos = e.Location
            End If
        End Sub

        Private Sub IMSSheet_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseUp
            If e.Button = MouseButtons.Left Then IsDraggingForm = False
        End Sub

        Private Sub IMSSheet_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseMove
            If IsDraggingForm Then
                Dim temp As Point = New Point(Me.Location + (e.Location - MousePos))
                Me.Location = temp
                temp = Nothing
            End If
        End Sub

        Private Sub onClose(sender As Object, e As EventArgs) Handles bt_Close.Click
            Me.Close()
        End Sub


        Private Sub bt_minimize_Click(sender As Object, e As EventArgs) Handles bt_minimize.Click
            Me.WindowState = FormWindowState.Minimized
        End Sub

        Private Sub bt_Close_MouseHover(sender As Object, e As EventArgs) Handles bt_Close.MouseHover

        End Sub

        Private Sub bt_minimize_MouseHover(sender As Object, e As EventArgs) Handles bt_minimize.MouseHover

        End Sub
    End Class

有趣的是，如果在运行程序之前，我的Messagestable中已经有一些新消息，它们将正确显示。 如果我使用Form.ShowDialog显示图纸，它也可以工作，但不是我想要的工作方式

---

由于我没有主意，希望您能帮助我。

您遇到了问题，因为SqlDependency的更改事件发生在您的UI线程所在的另一个线程上。从：

OnChange事件可能在与 启动命令执行的线程

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在非UI线程上调用sheet.Show时，Show将锁定，因为没有消息循环来处理UI事件。在ImsMain上使用可在UI线程上创建和显示ImsSheet。

在show调用上设置断点。当它中断时，使用Debug+Windows+Threads查看代码在哪个线程上运行。很有可能您会发现它不在程序的主UI线程上。这会让身体像门钉一样死掉。您需要使用Control.BeginInvoke使代码在UI线程上运行，而窗体有可能在该线程上运行。您的Catch块是否会捕获一个异常，而您无法看到，因为您正在使用Console.Writeline和窗体应用程序？尝试改用MessageBox.Showex.Message。谢谢。。我要试试你说的@Tinstaaff我已经尝试捕捉任何异常，但没有任何异常。。。你是对的，我现在使用的是调试而不是控制台。我必须尝试一下，但似乎这可能是问题所在。