如何在mysql查询执行成功时使用'try catch finally'块来显示消息

Question

我一直在C＃Windows窗体的代码中使用'try catch'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finally块中，我编写了一个消息框，显示数据库何时成功更新。

如果没有错误信息，它一切正常。成功消息显示。

但是，如果出现错误，则会显示catch块中的错误消息，然后显示finally块中的成功消息。

有谁知道解决方案让程序在mysql更新时显示错误消息或成功消息吗？

谢谢，

彼得

下面是一个代码示例：

私人无效btnUpdateEmployeeTable_Click（对象发件人，EventArgs的）//更新记录在雇员表 { 字符串MyConnection的= @” server = localhost; database = shopdb; username = **; password = **; convert zero 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"); 


     } 
    } 

Answer 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，它将永远不会执行。

 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 
     } 

    }