附加信息：无效的操作。连接已关闭。

问题描述

我在数据库中有两个表。我正在使用这些表来探索事务，插入，更新，删除，回滚和提交的应用程序。我有四个文本框两个到每个表和一个命令
按钮。我试图插入这些表并得到以下"附加信息：无效的操作。连接已关闭。 "带下划线的声明中的例外情况。我将非常感谢所有帮助。我的代码是
显示在下面

 Private Sub btnTransaction_Click(sender As Object, e As EventArgs) Handles btnTransaction.Click
        Using connection As New OleDbConnection(connstr)
            Dim Cmd As New oledbCommand
            Dim transaction As oledbtransaction
            'connection to New oledb Connection
            Cmd.connection = connection
            'open connection and execute transaction
            Try
                connection.open()

            Catch ex As Exception
                'Start Local connection
                transaction = connection.BeginTransaction(IsolationLevel.ReadCommitted)
                'assign transaction Object to local 
                Cmd.connection = connection
                Cmd.Transaction = transaction
                'execute the commands
                Cmd.commandtext = "INSERT INTO RelInfo(Surname, FirstName) Value (@SName, @FName)"
                Cmd.Parameters.AddWithValue("@SName", txtSurname.Text)
                Cmd.Parameters.AddWithValue("@FName", txtFirstName.Text)
                Cmd.ExecuteNonQuery()

                Cmd.CommandText = "INSERT INTO StudentInfo(SName, FName) Value (@SName, @FName)"
                Cmd.Parameters.AddWithValue("@SName", txtSName.Text)
                Cmd.Parameters.AddWithValue("@FName", txtFName.Text)
                Cmd.ExecuteNonQuery()

                'commit transaction
                transaction.Commit()
                MsgBox("Both Records Are Written to the database")
                Console.WriteLine(ex.Message)
                'Try to rollback the transaction
                Try
                    transaction.Rollback()
                Catch
                    ' do nothing transaction is not active anymore

                End Try
            End Try
        End Using
        Dim response As DialogResult = MessageBox.Show("Already been executed." &
                        Environment.NewLine & _
                        "Proceed with transaction?", "Performing transanction", _
                        MessageBoxButtons.YesNo)
            End Sub
End Class

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