问题描述

我正在尝试在我的 vb.net 应用程序中实现 sqldependency:

I'm trying to implement sqldependency in my vb.net application as per:

http://www.dreamincode.net/forums/topic/156991-using-sqldependency-to-monitor-sql-database-changes/

我在调用代码时遇到问题，当收到通知时，应用程序锁定且没有错误.(当通过委托调用 MyOnChanged 时)

I'm having problems with the involking code, when a notification is recieved the application locks up with no errors. (When MyOnChanged is called via the deligate)

我是否在 C# > VB.net 转换中犯了错误?

Have I made a mistake in my C# > VB.net conversion?

  Private Sub GetNames()
    Dim connectionString As String = "String..."
    ListView1.Items.Clear()

    SqlDependency.[Stop](connectionString)
    SqlDependency.Start(connectionString)

    Using cn As New SqlConnection(connectionString)
        Using cmd As SqlCommand = cn.CreateCommand()
            cmd.CommandType = CommandType.Text
            cmd.CommandText = "SELECT [finish_time], [file_name] FROM dbo.[log_table];"

            cmd.Notification = Nothing

            Dim dep As New SqlDependency(cmd)

            AddHandler dep.OnChange, New OnChangeEventHandler(AddressOf MyOnChanged)

            cn.Open()

            Using dr As SqlDataReader = cmd.ExecuteReader()
                While dr.Read()

                    Dim ls As New ListViewItem(dr.Item("finish_time").ToString.Trim())
                    ls.SubItems.Add(dr.Item("file_name").ToString.Trim())
                    ListView1.Items.Add(ls)

                End While
            End Using
        End Using
    End Using
End Sub




Private Sub MyOnChanged(ByVal sender As Object, ByVal e As SqlNotificationEventArgs)
    If ListView1.InvokeRequired Then
        ListView1.Invoke(New MethodInvoker(AddressOf GetNames))
    Else
        GetNames()
    End If
    Dim dep As SqlDependency = TryCast(sender, SqlDependency)
    AddHandler dep.OnChange, New OnChangeEventHandler(AddressOf MyOnChanged)
End Sub

推荐答案

按照 Merlyn 的建议，我使用 .NET 反射器来计算正确的 .net 转换:

As Merlyn recommended, I used .NET reflector to work out the proper .net conversion:

Private Sub MyOnChanged(ByVal sender As Object, ByVal e As SqlNotificationEventArgs)
    If MyBase.InvokeRequired Then
        Me.LVFTPXfers.BeginInvoke(New MethodInvoker(AddressOf Me.GetNames))
    Else
        Me.GetNames()
    End If
    Dim dependency As SqlDependency = TryCast(sender, SqlDependency)
    RemoveHandler dependency.OnChange, New OnChangeEventHandler(AddressOf Me.MyOnChanged)
End Sub

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