mysql查询成功执行时如何使用'try catch finally'块显示消息答案

【问题标题】：how to use 'try catch finally' block to display message when mysql query is executed successfullymysql查询成功执行时如何使用'try catch finally'块显示消息
【发布时间】：2014-07-06 00:42:48
【问题描述】：

我一直在 C# Windows 窗体的代码中使用“try catch finally”来查询 MySQL 数据库。该代码运行良好：当 catch 块标记错误时，消息框将显示错误消息。

在 finally 块中，我编写了一个消息框，它将在数据库成功更新时显示。

如果没有错误消息，一切正常。显示成功消息。

但是如果有错误，会显示catch块中的错误信息，然后是finally块中的成功信息。

有没有人知道在更新 mysql 时让程序显示错误消息或成功消息的解决方案？

谢谢，

彼得

这是一个代码示例：

private void btnUpdateEmployeeTable_Click(object sender, EventArgs e) //更新Employee表中的记录 { String myConnection = @"server=localhost; database=shopdb; username=**; password=**; 转零 datetime=True"; MySqlConnection Connect = null;

        try
        {
            Connect = new MySqlConnection(myConnection);
            Connect.Open(); //Open the connection

            //This is the mysql command that we will query into the db.
            //It uses Prepared statements and the Placeholders for faster, more secure processing.

            String updateQuery = "UPDATE employee SET emp_lName = @empLastName, emp_fName = @empFirstName WHERE emp_number = @empNum";

            MySqlCommand cmdInsertEmployeeToDataBase = new MySqlCommand(updateQuery, Connect);
            cmdInsertEmployeeToDataBase.Prepare();

            //Bind the value to the placeholder               

            cmdInsertEmployeeToDataBase.Parameters.AddWithValue("@empNum", this.txtEmployeeNo.Text);
            cmdInsertEmployeeToDataBase.Parameters.AddWithValue("@empLastName", this.txtEmployeeLastName.Text);
            cmdInsertEmployeeToDataBase.Parameters.AddWithValue("@empFirstName", this.txtEmployeeFirstName.Text);                

            cmdInsertEmployeeToDataBase.ExecuteNonQuery(); //Execute the mysql command 


        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message + "\nDatabase could not be updated \n" + "Please try again");

        }
        finally
        {
            if (Connect != null)
            {
                Connect.Close(); //Close the connection
            }


            MessageBox.Show("Database update successful");


        }
    }

【问题讨论】：

工作点亮了魅力！简单，出色的解决方案。谢谢！！

标签： error-handling try-catch-finally

【解决方案1】：

您可以轻松地将成功代码向上移动。如果在MessageBox.Show("Database update successful"); 行之前抛出异常，那么它将永远不会被执行。

     try
     {
        Connect = new MySqlConnection(myConnection);
        Connect.Open(); //Open the connection

        //This is the mysql command that we will query into the db.
        //It uses Prepared statements and the Placeholders for faster, more secure processing.

        String updateQuery = "UPDATE employee SET emp_lName = @empLastName, emp_fName = @empFirstName WHERE emp_number = @empNum";

        MySqlCommand cmdInsertEmployeeToDataBase = new MySqlCommand(updateQuery, Connect);
        cmdInsertEmployeeToDataBase.Prepare();

        //Bind the value to the placeholder               

        cmdInsertEmployeeToDataBase.Parameters.AddWithValue("@empNum", this.txtEmployeeNo.Text);
        cmdInsertEmployeeToDataBase.Parameters.AddWithValue("@empLastName", this.txtEmployeeLastName.Text);
        cmdInsertEmployeeToDataBase.Parameters.AddWithValue("@empFirstName", this.txtEmployeeFirstName.Text);

        cmdInsertEmployeeToDataBase.ExecuteNonQuery(); //Execute the mysql command 

        MessageBox.Show("Database update successful");

     }
     catch (Exception ex)
     {
        MessageBox.Show(ex.Message + "\nDatabase could not be updated \n" + "Please try again");

     }
     finally
     {
        if (Connect != null)
        {
           Connect.Close(); //Close the connection
        }

     }

【讨论】：