当mysql查询成功执行时，如何使用“try catch finally”块显示消息

Question

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

在最后一个块中，我编写了一个消息框，它将显示数据库成功更新的时间。

如果没有错误消息，则一切正常。成功消息显示。

但是如果有错误，就会显示catch块中的错误消息，然后显示finally块中的成功消息。

有人知道一个解决方案，让程序在mysql更新时显示错误消息或成功消息吗？

谢谢，

耗尽

下面是一个代码示例:

私有无效btnUpdateEmployeeTable_Click（对象发送方，事件Args e） //更新员工表中的记录 { 字符串 myConnection = @“服务器=本地主机; 数据库=shopdb; 用户名=**; 密码=**; 转换零日期时间=True”;我的连接 = 空;

        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");


        }
    }

Answer 1

您可以轻松地将成功代码向上移动。如果在MessageBox.Show（"数据库更新成功"）；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
        }

     }