ADO.NET Cookbook

2.13. Executing SQL Server User-Defined Scalar Functions

Problem

Your SQL Server 2000 database includes a user-defined function that returns a scalar value. You want to retrieve the value from this function using ADO.NET.

Solution

Invoke the function as you would a query or stored procedure.

The sample code, as shown in Example 2-16, uses a single SQL Server function:

ExtendedPrice

Calculates and returns the extended price for an order line item based on the unit price, quantity, and discount.

Example 2-16. SQL Server function: ExtendedPrice

CREATE FUNCTION dbo.ExtendedPrice
(
    @UnitPrice money,
    @Quantity smallint,
    @Discount real
)
RETURNS money
AS

BEGIN
    RETURN ((@UnitPrice * @Quantity) * (1 - @Discount))
END

The sample code defines a SQL statement that uses the ExtendedPrice user-defined function. The statement is used by a DataAdapter to fill a DataTable with all records from the Order Details table in Northwind together with the extended price calculation for each record. The default view of the table is bound to a data grid on the form.

The C# code is shown in Example 2-17.

Example 2-17. File: ScalarFunctionForm.cs

// Namespaces, variables, and constants using System; using System.Configuration; using System.Data; using System.Data.SqlClient; // . . . String sqlText = "SELECT *, " + "dbo.ExtendedPrice(UnitPrice, Quantity, Discount) ExtendedPrice " + "FROM [Order Details]"; // Create DataAdapter and fill the table. SqlDataAdapter da = new SqlDataAdapter(sqlText, ConfigurationSettings.AppSettings["Sql_ConnectString"]); ...