Unique Key constraints for multiple columns in Entity Framework
constraints, ef-code-first, entity-framework, multiple-columns, unique-key
Solution
With Entity Framework 6.1, you can now do this:
[Index("IX_FirstAndSecond", 1, IsUnique = true)]
public int FirstColumn { get; set; }
[Index("IX_FirstAndSecond", 2, IsUnique = true)]
public int SecondColumn { get; set; }
The second parameter in the attribute is where you can specify the order of the columns in the index. More information: MSDN
Problem
I'm using Entity Framework 5.0 Code First; ``` public class Entity { [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)] public string EntityId { get; set;} public int FirstColumn { get; set;} public int SecondColumn { get; set;} } ``` I want to make the combination between `FirstColumn` and `SecondColumn` as unique. Example: ``` Id FirstColumn SecondColumn 1 1 1 = OK 2 2 1 = OK 3 3 3 = OK 5 3 1 = THIS OK 4 3 3 = GRRRRR! HERE ERROR ``` Is there anyway to do that?