vb.net polling SQL Server每秒一次造成超時

Question

我被要求做一個系統，每秒輪詢一個數據庫中的一個表，並且它是否符合滿足標準啓動操作來處理該行的一行。

我已經完成了這項工作，但每隔一段時間我都會遇到超時異常。我有一個WPF應用程序，我有一個線程在後臺運行。這個線程有一個循環，並在循環結束時睡一秒鐘。連接到數據庫在「using」子句中打開。

下面是我的線程子：

Private Sub PollDatabase() 
    While m_StopThread = False 
     Try 
     Dim listOfRows As List(Of DataObject) = db.GetDataObjects() 

     ... Do something with the rows ... 

     Catch ex As Exception 
      m_log.WriteLine(ex.ToString()) 
     End Try 
    Thread.Sleep(1000) 
    End While 
End Sub 

我的SQL函數如下所示：

Public Function GetDataObjects() As List(Of DataObject) 
    Dim result As New List(Of DataObject) 
    Dim sb As New StringBuilder("... the sql query ...") 

    Using cnn = New SqlConnection(_connectionString) 
     cnn.Open() 
     Using cmd = New SqlCommand(sb.ToString(), cnn) 
      cmd.CommandTimeout = 0 
      Using DataReader As SqlDataReader = cmd.ExecuteReader() 
      Do While DataReader.Read() 
       ... read the columns from table 
        to the dataobject ... 
       result.Add(DataObject) 
      Loop 
      End Using 
     End Using 
    End Using 
    Return result 
End Function 

現在似乎什麼隨機我的日誌有一個超時異常：

System.Data.SqlClient.SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. 
... 
at System.Data.SqlClient.SqlConnection.Open() 

我的問題是：這樣做是否存在這樣做的方式？或者我在這裏做了一些根本性的錯誤？當然如果有人有解決這個問題的建議。

編輯：

我試着用SQL函數有點不同的方法。當我的應用程序啓動並拋棄「使用」子句時，我現在打開一個連接。所以我現在的功能看起來像這樣：

Public Function GetDataObjects() As List(Of DataObject) 
    Dim result As New List(Of DataObject) 
    Dim sb As New StringBuilder("... the sql query ...") 
    _sqlCmd.CommandText = sb.ToString() 

    Using DataReader As SqlDataReader = _sqlCmd.ExecuteReader() 
     Do While DataReader.Read() 
     ... fill the list with objects ... 
     Loop 
    End Using 

    Return result 
End Function 

我的日誌是乾淨的表單錯誤。那麼是否有什麼問題在一秒鐘內打開與服務器的連接？

編輯：

我已經做了很多測試，現在找出問題所在。我發現，多次連接到服務器並不會造成任何問題。在連接後添加select語句也沒有。但是當我真正實現一個功能，其中是完整的閱讀器部分，並返回我的結果時，我遇到了超時問題。這裏有兩個例子。

這不是導致問題：

Private Sub Window_Loaded(sender As System.Object, e As System.Windows.RoutedEventArgs) 
    Me.DataContext = Me 
    m_Thread = New Thread(AddressOf ConnectionTestFunction) 
    m_Thread.IsBackground = True 
    m_Thread.Start() 
End Sub 

Private Sub ConnectionTestFunction() 
    While m_stopThread = False 
     Try 
      m_log.WriteLine("GetData (" & m_ThreadCounter & ")") 
      Using cnn As SqlConnection = New SqlConnection("Data Source=server;Initial Catalog=db;Integrated Security=True;MultipleActiveResultSets=True") 
       cnn.Open() 
       Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Data", cnn) 
        Using DataReader As SqlDataReader = cmd.ExecuteReader() 
         Do While DataReader.Read() 
         Loop 
        End Using 
       End Using 
      End Using 
     Catch ex As Exception 
      m_log.WriteLine(ex.ToString()) 
     End Try 
     m_ThreadCounter += 1 
     Thread.Sleep(1000) 
    End While 
End Sub 

這導致超時錯誤：

Private Sub Window_Loaded(sender As System.Object, e As System.Windows.RoutedEventArgs) 
    Me.DataContext = Me 
    m_Thread = New Thread(AddressOf ConnectionTestFunction) 
    m_Thread.IsBackground = True 
    m_Thread.Start() 
End Sub 

Private Sub ConnectionTestFunction() 
    While m_stopThread = False 
     Try 
      m_log.WriteLine("GetData (" & m_ThreadCounter & ")") 
      Dim datarows As List(Of Data) = Me.GetData() 
     Catch ex As Exception 
      m_log.WriteLine(ex.ToString()) 
     End Try 
     m_ThreadCounter += 1 
     Thread.Sleep(1000) 
    End While 
End Sub 

Private Function GetData() As List(Of Data) 
    Dim result As New List(Of Data) 
    Using cnn As SqlConnection = New SqlConnection("Data Source=server;Initial Catalog=db;Integrated Security=True;MultipleActiveResultSets=True") 
     cnn.Open() 
     Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Data", cnn) 
      Using DataReader As SqlDataReader = cmd.ExecuteReader() 
       Do While DataReader.Read() 
        Dim d As New Data() 
        d.DataId = DataReader("DataId") 
        ... etc fields about 10 of them ... 
        result.Add(d) 
       Loop 
      End Using 
     End Using 
    End Using 
    Return result 
End Function 

我真的很高興，如果有人對此有任何的想法......我不得不承認我現在很困惑。

Answer 1

也許，您的代碼完成所需的時間比連接的默認超時值要長。嘗試在創建Sql連接時指定超時值。確保它比您的代碼需要完成的時間更長。

Answer 2

這種方法看起來不太好..而不是彙集，爲什麼不響應新數據時呢？你可以使用觸發器或SqlDependency？

http://dotnet.dzone.com/articles/c-sqldependency-monitoring