无法在VB.NET中关闭OledbDataReader到Sybase数据库

Question

从中读取数据后，我似乎无法关闭OledbDataReader对象。这是相关的代码 -

Dim conSyBase As New OleDb.OleDbConnection("Provider=Sybase.ASEOLEDBProvider.2;Server Name=xx.xx.xx.xx;Server Port Address=5000;Initial Catalog=xxxxxxxxxx;User ID=xxxxxxxx;Password=xxxxxxxxx;")

conSyBase.Open()

Dim cmdSyBase As New OleDb.OleDbCommand("MySQLStatement", conSyBase)
Dim drSyBase As OleDb.OleDbDataReader = cmdSyBase.ExecuteReader

Try

    While drSyBase.Read
     /*Do some stuff with the data here */

    End While

Catch ex As Exception

    NotifyError(ex, "Read failed.")

End Try

drSyBase.Close() /* CODE HANGS HERE */
conSyBase.Close()
drSyBase.Dispose()
cmdSyBase.Dispose()
conSyBase.Dispose()

控制台应用程序只是在我尝试关闭阅读器时挂起。打开和关闭连接不是问题，因此有没有人对可能导致此问题的想法有任何想法？

Answer 1

我找到了答案！

在

drSyBase.Close()

您需要调用Command对象的cancel方法

cmdSyBase.Cancel()

我认为这可能是Sybase数据库特有的

Answer 2

这是一个长镜头，但尝试在Try的Finally块中移动.Close（）和.Dispose（）行。像这样：

Dim conSyBase As New OleDb.OleDbConnection("Provider=Sybase.ASEOLEDBProvider.2;Server Name=xx.xx.xx.xx;Server Port Address=5000;Initial Catalog=xxxxxxxxxx;User ID=xxxxxxxx;Password=xxxxxxxxx;")
conSyBase.Open()
Dim cmdSyBase As New OleDb.OleDbCommand("MySQLStatement", conSyBase)
Dim drSyBase As OleDb.OleDbDataReader = cmdSyBase.ExecuteReader
Try
  While drSyBase.Read
   /*Do some stuff with the data here */
  End While
Catch ex As Exception 
  NotifyError(ex, "Read failed.")
Finally
  drSyBase.Close() 
  conSyBase.Close()
  drSyBase.Dispose()
  cmdSyBase.Dispose()
  conSyBase.Dispose()
End Try

Answer 3

我使用VB.NET已经有一段时间了，但在C＃中处理此问题最安全的方法是使用“使用”言。

它就像一个隐式try-catch ，它确保所有资源在“使用”时被关闭/取消和处理。结束。

using (OleDb.OleDbConnection connection = new OleDb.OleDbConnection(connectionString)) 
{
    DoDataAccessStuff();
} // Your resource(s) are killed, disposed and all that

更新：找到关于在VB.NET 2.0中使用语句，希望它有所帮助。

Using conSyBase As New OleDb.OleDbConnection("Provider=Sybase.ASEOLEDBProvider.2;Server Name=xx.xx.xx.xx;Server Port Address=5000;Initial Catalog=xxxxxxxxxx;User ID=xxxxxxxx;Password=xxxxxxxxx;"), _
     cmdSyBase As New OleDb.OleDbCommand("MySQLStatement", conSyBase) 

    conSyBase.Open()
    Dim drSyBase As OleDb.OleDbDataReader = cmdSyBase.ExecuteReader

    Try
        While drSyBase.Read()

            '...'

        End While
    Catch ex As Exception
        NotifyError(ex, "Read failed.")
    End Try

    cmdSyBase.Cancel()
End Using