ConcurrencyCheck Attribute:
ConcurrencyCheck attribute can be applied to a property of a domain class. Code First takes the value of a column in "where" clause when EF executes update command for the table. You can use ConcurrencyCheck attribute when you want to use existing column for concurrency check and not a separate timestamp column for concurrency.
Consider the following example.
using System.ComponentModel.DataAnnotations; public class Student { public Student() { } public int StudentId { get; set; } [ConcurrencyCheck] public string StudentName { get; set; } }
As you can see in the above example, ConcurrencyCheck attribute is applied to existing StudentName property of the Student class. So, Code-First will include StudentName column in update command to check for optimistic concurrency.
exec sp_executesql N‘UPDATE [dbo].[Students] SET [StudentName] = @0 WHERE (([StudentId] = @1) AND ([StudentName] = @2)) ‘,N‘@0 nvarchar(max) ,@1 int,@2 nvarchar(max) ‘,@0=N‘Steve‘,@1=1,@2=N‘Bill‘ go
Note that TimeStamp attribute can only be applied to a single byte array property in a class, whereas ConcurrencyCheck attribute can be applied to any number of properties with any datatype.