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Passing Null Values to Parameters

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[ Team LiB ] Recipe 2.14 Passing Null Values to Parameters Problem You need to pass a null value to a parameter. Solution Use the System.DbNull.Value static value. The sample code, as shown in Example 2-18, uses a single stored procedure | Team LiB Recipe 2.14 Passing Null Values to Parameters Problem You need to pass a null value to a parameter. Solution Use the System.DbNull.Value static value. The sample code as shown in Example 2-18 uses a single stored procedure SP0214_NullParameter Accepts a single parameter and a returns one-row result set containing a single value indicating whether that input parameter was null. Example 2-18. Stored procedure SP0214_NullParameter CREATE PROCEDURE SP0214_NullParameter @ValueIn int AS if @ValueIn is null select 1 as IsParameterNull else select 0 as IsParameterNull return 0 The sample code contains two event handlers Go Button.Click Creates a stored procedure command for SP0214_NullParameter and defines its single input parameter. The input parameter is set to System.DbNull.Value if the user has checked the Null Parameter check box on the form otherwise it is set to the value that the user has entered in the Parameter text box. The stored procedure is executed using the ExecuteScalar method and the value returned indicates whether the input parameter for the stored procedure is null. Null Parameter CheckBox.CheckedChange Clears the value of the Parameter text box if checked and enables the Parameter text box if not checked. The C code is shown in Example 2-19. Example 2-19. File NullParameterForm.es Namespaces variables and constants using System using System.Configuration using System.Data using System.Data.SqlClient . . . private void goButton_Click object sender System.EventArgs e Create the connection. SqlConnection conn new SqlConnection ConfigurationSettings.AppSettings S ql_ConnectString Create the stored procedure command. SqlCommand cmd new SqlCommand SP0214_NullParameter conn cmd.CommandType CommandType.StoredProcedure Define the parameter. cmd.Parameters.Add @ValueIn SqlDbType.Int Set the value of the paramter. if isNullCheckBox.Checked cmd.Parameters 0 .Value System.DBNull.Value else cmd.Parameters 0 .Value parameterTextBox.Text Retrieve whether .