辅助类备忘录之数据库监控-Sqldependency

通用类：

Imports System.Data.SqlClient
Public Class DataBaseMonitor
    Dim _connectionstring As String = My.Settings.RecordConnectionString
    Dim conn As SqlConnection
    Dim _cmd As String
    Dim _queue As String = String.Empty
    Public Event OnChange(sender As Object, e As SqlNotificationEventArgs)

    Public Property ConnectionString As String
        Get
            Return _connectionstring
        End Get
        Set(value As String)
            _connectionstring = value
            conn = New SqlConnection(value)
        End Set
    End Property

    Public Property CommandText As String
        Get
            Return _cmd
        End Get
        Set(value As String)
            _cmd = value
        End Set
    End Property

    Public Property Queue As String
        Get
            Return _queue
        End Get
        Set(value As String)
            _queue = value
        End Set
    End Property

    Sub New(cmdtext As String)
        ConnectionString = _connectionstring
        CommandText = cmdtext
    End Sub

    Sub New(cmdtext As String, connstring As String)
        ConnectionString = connstring
        CommandText = cmdtext
    End Sub

    Public Sub Start()
        If Queue = String.Empty Then
            SqlDependency.Start(ConnectionString)
        Else
            SqlDependency.Start(ConnectionString, Queue)
        End If
        addOne()
    End Sub

    Private Sub dependency_OnChange(sender As Object, e As SqlNotificationEventArgs)
        RaiseEvent OnChange(sender, e)
        addOne()
    End Sub
    Private Sub addOne()
        If conn.State <> ConnectionState.Open Then
            conn.Open()
        End If
        Dim Command As New SqlCommand(CommandText, conn)
        Dim dependency = New SqlDependency(Command)
        Command.ExecuteNonQuery()
        AddHandler dependency.OnChange, AddressOf dependency_OnChange
    End Sub

    Public Sub StopMonitor()
        If Queue = String.Empty Then
            SqlDependency.Stop(ConnectionString)
        Else
            SqlDependency.Stop(ConnectionString, Queue)
        End If
        If conn.State <> ConnectionState.Closed Then
            conn.Close()
        End If
    End Sub

    Public Sub Dispose()
        conn.Dispose()
    End Sub

End Class

具体类：

Imports System.Data.SqlClient

Public Class CopyLogMonitor
    Public Event OnChange(sender As Object, e As SqlNotificationEventArgs)
    WithEvents monitor As DAL.DataBaseMonitor
    Sub New()
        Dim sql As String = "select 住院号,次数,嘉禾登记 from dbo.recordcopylogs where 复印时间>'20170101'"
        monitor = New DAL.DataBaseMonitor(sql)
        monitor.Start()
    End Sub

    Private Sub monitor_OnChange(sender As Object, e As SqlNotificationEventArgs) Handles monitor.OnChange
        If e.Type = SqlNotificationType.Change Then
            RaiseEvent OnChange(sender, e)
        End If
    End Sub

    Public Sub StopMonitor()
        monitor.StopMonitor()
    End Sub
End Class