How to: Represent Primary Keys (LINQ to SQL)
Use the LINQ to SQL IsPrimaryKey property on the ColumnAttribute attribute to designate a property or field to represent the primary key for a database column.
For code examples, see IsPrimaryKey.
Note
LINQ to SQL does not support computed columns as primary keys.
To designate a property or field as a primary key
Add the IsPrimaryKey property to the ColumnAttribute attribute.
Specify the value as true.
See Also
Concepts
Other Resources
How to: Customize Entity Classes by Using the Code Editor (LINQ to SQL)