基本上我的代码基于这里 http://www.dreamincode.net/forums/topic/185244-using-sqldependency-to-monitor-sql-database-changes/
目前的情况是我有 2 个表希望监控，所以我简单地使用第一个 sqldependancy 复制另一个类似的代码，但它失败了，似乎最新的 sqldependancy 将替换以前的 sqldependancy 函数。
这是我的代码
Public Sub GetNames()
If Not DoesUserHavePermission() Then
Return
End If
lbQueue.Items.Clear()
' You must stop the dependency before starting a new one.
' You must start the dependency when creating a new one.
Dim connectionString As String = GetConnectionString()
SqlDependency.Stop(connectionString)
SqlDependency.Start(connectionString)
Using cn As SqlConnection = New SqlConnection(connectionString)
Using cmd As SqlCommand = cn.CreateCommand()
cmd.CommandType = CommandType.Text
cmd.CommandText = "SELECT PatientID FROM dbo.[patient_queue]"
cmd.Notification = Nothing
' creates a new dependency for the SqlCommand
Dim dep As SqlDependency = New SqlDependency(cmd)
' creates an event handler for the notification of data changes in the database
AddHandler dep.OnChange, AddressOf dep_onchange
cn.Open()
Using dr As SqlDataReader = cmd.ExecuteReader()
While dr.Read()
lbQueue.Items.Add(dr.GetInt32(0))
doctor.lbqueue.items.add(dr.GetInt32(0))
End While
End Using
End Using
End Using
End Sub
Private Sub dep_onchange(ByVal sender As System.Object, ByVal e As System.Data.SqlClient.SqlNotificationEventArgs)
' this event is run asynchronously so you will need to invoke to run on the UI thread(if required)
If Me.InvokeRequired Then
lbQueue.BeginInvoke(New MethodInvoker(AddressOf GetNames))
My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Asterisk)
Else
GetNames()
End If
' this will remove the event handler since the dependency is only for a single notification
Dim dep As SqlDependency = DirectCast(sender, SqlDependency)
RemoveHandler dep.OnChange, AddressOf dep_onchange
End Sub
Public Sub GetMedID()
If Not DoesUserHavePermission() Then
Return
End If
lbMedQueue.Items.Clear()
' You must stop the dependency before starting a new one.
' You must start the dependency when creating a new one.
Dim connectionString As String = GetConnectionString()
SqlDependency.Stop(connectionString)
SqlDependency.Start(connectionString)
Using cn As SqlConnection = New SqlConnection(connectionString)
Using cmd As SqlCommand = cn.CreateCommand()
cmd.CommandType = CommandType.Text
cmd.CommandText = "SELECT RecordID FROM dbo.[medicine_queue]"
cmd.Notification = Nothing
' creates a new dependency for the SqlCommand
Dim dep As SqlDependency = New SqlDependency(cmd)
' creates an event handler for the notification of data changes in the database
AddHandler dep.OnChange, AddressOf dep_onchange2
cn.Open()
Using dr As SqlDataReader = cmd.ExecuteReader()
While dr.Read()
lbMedQueue.Items.Add(dr.GetInt32(0))
End While
End Using
End Using
End Using
End Sub
Private Sub dep_onchange2(ByVal sender As System.Object, ByVal e As System.Data.SqlClient.SqlNotificationEventArgs)
' this event is run asynchronously so you will need to invoke to run on the UI thread(if required)
If Me.InvokeRequired Then
lbMedQueue.BeginInvoke(New MethodInvoker(AddressOf GetMedID))
My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Asterisk)
Else
GetMedID()
End If
' this will remove the event handler since the dependency is only for a single notification
Dim dep As SqlDependency = DirectCast(sender, SqlDependency)
RemoveHandler dep.OnChange, AddressOf dep_onchange2
End Sub
最后我在加载表单上调用了 GetNames，GetMedID，它工作正常，只是 GetMedID 正在运行，并且 GetNames 在 onchanged 时不会触发事件。