You can set a column in a DataTable to be an auto-incrementing primary key in order to ensure a unique value for each row in the table. However, you may have multiple clients for your application, and each of those clients can be working with a separate instance of the DataTable. In this case, you might end up with duplicate values between the separate instances of the DataTable. Because all your clients are working with a single data source, you can resolve this conflict by letting the data source define the auto-incremented value. To accomplish this you use Identity fields in Microsoft SQL Server
Using the data source to populate an Identity or Autonumber column for a new row added to a DataSet creates a unique situation because the DataSet has no direct connection to the data source. As a result, the DataSet is unaware of any values generated automatically by the data source. However, with a data source that can create stored procedures with output parameters, such as Microsoft SQL Server, you can specify the automatically generated values, such as a new identity value, as an output parameter and use the DataAdapter to map that value back to the column in the DataSet.
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