Question

我用

vb.NET 2013
Framework 2.0
来自.Net Framework的ODBC连接
ODBC MySQL Connector 3.51

有时候，但并非总是如此，当我查询数据库时程序没有响应而且根本没有错误。

重新启动应用程序并再次执行完全相同的操作后，一切正常。

        Function GetData(ByVal xxx1 As Integer, ByVal xxx2 As DateTime, ByVal xxx3 As DateTime) As DataTable
        Dim dt As DataTable = NewDT.GetData

        Try
            SyncLock Master_Con
                Using cmd As New OdbcCommand(myCmdStr, Master_Con)
                    cmd.CommandTimeout = SQLCmd.intCmdTimeout '3
                    cmd.Parameters.Add("xxx1", OdbcType.Int).Value = xxx1
                    cmd.Parameters.Add("xxx2", OdbcType.NVarChar).Value = xxx2
                    cmd.Parameters.Add("xxx3", OdbcType.NVarChar).Value = xxx3
                    Using dr As OdbcDataReader = cmd.ExecuteReader
                        If dr.HasRows Then
                            Dim rowcount As Integer = 0
                            While dr.Read()
                                dt.Rows.Add()
                                For count As Integer = 0 To (dr.FieldCount - 1)
                                    dt.Rows(rowcount).Item(count) = dr(count)
                                Next
                                rowcount = rowcount + 1
                            End While
                        End If
                    End Using
                End Using
            End SyncLock

        Catch OdbcEx As OdbcException
            MessageBox.Show("ODBC-Fehler bei Funktion 'GetData'. " & vbCrLf & vbCrLf & OdbcEx.Message, "App", MessageBoxButtons.OK, MessageBoxIcon.Error)

        Catch ex As Exception
            MessageBox.Show("Systemfehler bei Funktion 'GetData'. " & vbCrLf & vbCrLf & ex.Message, "App", MessageBoxButtons.OK, MessageBoxIcon.Error)

        End Try

        Debug.WriteLine("done.")
        Return dt

    End Function

我的日志说的是这样的：

GetData (28.08.15 - 28.08.15)... done.
GetData2 (28.08.15)... done.
DelData... done.
GetData (28.08.15 - 28.08.15)... done.
GetData2 (28.08.15)... done.
GetData (27.08.15 - 27.08.15)... done.
GetData2 (27.08.15)... done.
GetData (26.08.15 - 26.08.15)...

程序在运行cmd.ExecuteReader时一直没响应。因为我以完全相同的方式运行命令多次，我猜测它与超时或mysql服务器/连接繁忙有关。

但是因为它永远不会引发错误/ odbc错误，它只会偶尔发生，然后我不知道如何解决它。

任何帮助都会很好！

Answer 1

The problem was about sometimes getting a deadlock.

It now works as it should after invoking the SQLCommand execution in a its own function.

Private Delegate Function ExecScalarDelegate(ByVal cmd As System.Data.Odbc.OdbcCommand, _ 
ByRef ReturnValue As Object) As Boolean

Private Shared Function ExecScalar(ByVal cmd As System.Data.Odbc.OdbcCommand, _ 
ByRef ReturnValue As Object) As Boolean
    ExecScalar = False

    SyncLock cmd.Connection
        ReturnValue = cmd.ExecuteScalar()
    End SyncLock
    Return True
End Function

有时VB.NET MySQL，但并不总是冻结整个应用程序

1 个答案: