Tài liệu Raising and Handling Stored Procedure Errors pptx

[ Team LiB ] Recipe 2.10 Raising and Handling Stored Procedure Errors Problem You want to catch and handle an error raised from a stored procedure. Solution Use a try . . . catch block to catch serious errors. Use the SqlConnection.InfoMessage event handler to catch informational and warning messages. The sample code, as shown in Example 2-11 , uses a single stored procedure and two event handlers: SP0210_Raiserror Accepts two input parameters specifying the severity and the state of an error and raises an error with the specified severity and state. Raise Error Button.Click Creates a connection and attaches a handler for warning and information messages from the SQL Server. A Command is created for the SP0210_Raiserror stored procedure and the input parameters are defined. The user-specified severity and state are assigned to the input parameters and the stored procedure command is executed within a try statement. SqlConnection.InfoMessage Called when a warning or informational message is raised by the SQL Server. Example 2-11. Stored procedure: SP0210_Raiserror CREATE PROCEDURE SP0210_Raiserror @Severity int, @State int = 1 AS if @Severity>=0 and @Severity <=18 RAISERROR ('Error of severity %d raised from SP 0210_Raiserror.', @Severity, @State, @Severity) if @Severity>=19 and @Severity<=25 RAISERROR ('Fatal error of severity %d raised from SP 0210_Raiserror.', @Severity, @State, @Severity) WITH LOG RETURN The C# code is shown in Example 2-12 . Example 2-12. File: RaiserrorForm.cs // Namespaces, variables, and constants using System; using System.Configuration; using System.Data; using System.Data.SqlClient; // . . . private void raiseErrorButton_Click(object sender, System.EventArgs e) { resultTextBox.Text = "Severity: " + severityTextBox.Text + Environment.NewLine + "State: " + stateTextBox.Text + Environment.NewLine + Environment.NewLine; // Create the connection. SqlConnection conn = new SqlConnection( ConfigurationSettings.AppSettings["Sql_ConnectString"]); // Attach handler for SqlInfoMessage events. conn.InfoMessage += new SqlInfoMessageEventHandler(conn_InfoMessage); // Define a stored procedure command and the parameters. SqlCommand cmd = new SqlCommand("SP0210_Raiserror", conn); cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.Add("@Severity", SqlDbType.Int); cmd.Parameters.Add("@State", SqlDbType.Int); // Set the value for the stored procedure parameters. cmd.Parameters["@Severity"].Value = severityTextBox.Text; cmd.Parameters["@State"].Value = stateTextBox.Text; // Open the connection. conn.Open( ); try { // Try to execute the stored procedure. cmd.ExecuteNonQuery( ); } catch(System.Data.SqlClient.SqlException ex) { // Catch SqlException errors. resultTextBox.Text += "ERROR: " + ex.Message; } catch(Exception ex) { // Catch other errors. resultTextBox.Text += "OTHER ERROR: " + ex.Message; } finally { // Close the connection. conn.Close( ); } } private void conn_InfoMessage(object sender, SqlInfoMessageEventArgs e) { resultTextBox.Text += "MESSAGE: " + e.Message; } Discussion Errors and messages are returned from a SQL Server stored procedure to a calling application using the RAISERROR (note the spelling) function. The error message severity levels are listed in Table 2-12 . Table 2-12. RAISERROR error message severity levels Severity level Description 0-10 Informational 11-16 Error which can be corrected by the user 17-19 Resource or system error 20-25 Fatal error indicating a system problem Severity levels greater than 20 result in the connection being closed. Since severity levels 10 or less are considered to be informational, they raise a SqlInfoMessageEvent rather than an error. This is handled by subscribing a SqlInfoMessageEventHandler to the InfoMessage event of the SqlConnection object. If the error has severity level 11 or greater, a SqlException is thrown by the SQL Server .NET data provider. For more information about the RAISERROR function, look up RAISERROR in SQL Server Books Online. [ Team LiB ] . Team LiB ] Recipe 2.10 Raising and Handling Stored Procedure Errors Problem You want to catch and handle an error raised from a stored procedure. Solution. SP0210_Raiserror stored procedure and the input parameters are defined. The user-specified severity and state are assigned to the input parameters and the stored procedure