ADO.NET Cookbook

2.21. Using Parameterized SQL Statements

Problem

You want to create and execute a SQL statement having parameters that are set dynamically.

Solution

Add parameters to the Command object’s Parameters collection.

The sample code contains two event handlers and one method:

Form.Load

Sets up the sample by creating a DataTable containing all Customers data from Northwind. The default view of the table is bound to a Customers data grid on the form. The handler for the CurrentCellChanged event of the data grid is called to initialize the grid containing Orders with the data for the row selected by default in the Customers data grid.

DataGrid.CurrentCellChanged

Gets the CustomerID from the data grid when the rows selected in the data grid changes and calls the LoadOrderGrid( ) method to update the Orders displayed to match the selected Customer.

LoadOrderGrid( )

This method defines a parameterized SQL statement. A Command is built from the statement and the single parameter, @CustomerID is created and set to the customerId argument passed into the method. The Command is used by a DataAdapter to fill a DataTable with the Orders for the specified Customer. The default view of the table is bound to the Customers data grid on the form.

The C# code is shown in Example 2-30.

Example 2-30. File: UsingParameterizedQueriesForm.cs

// Namespaces, variables, and constants using System; using System.Configuration; using System.Data; using System.Data.SqlClient; // Table name constants private const String CUSTOMERS_TABLE ...