ADO.NET Cookbook

4.2. Getting an Identity Column Value from SQL Server

Problem

When you add a row into a SQL Server table that has an identity column, the value assigned to the column in the DataTable is replaced by a value generated by the database. You need to retrieve the new value to keep the DataTable synchronized with the database.

Solution

There are two ways to synchronize identity values generated by the data source: use either the first returned record or the output parameters of a stored procedure.

The sample uses a single stored procedure:

InsertCategories

Used to add a new Categories record to the Northwind database. The stored procedure returns the CategoryId value generated by the data source as both an output parameter and in the first returned record.

The sample code contains two event handlers:

Form.Load

Sets up the sample by creating a DataTable and programmatically defining the schema to match the Categories table in Northwind. The AutoIncrementSeed and AutoIncrementStep property values are both set to -1 for the AutoIncrement primary key column, the CategoryID. A DataAdapter is created and used to fill the DataTable. The insert command and its parameters are defined for the DataAdapter so that new rows can be added to the data source and the CategoryID value generated by the data source can be retrieved using either the output parameter values or first returned record from the InsertCategories stored procedure. The default view of the table is bound to the data grid on the form.

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