how can create Unique Constraint with multi column with entityframework

问题

I'm use Entityframework Code First, and an EntityTypeConfiguration using fluent API. how can create Unique Constraint with multi column. for example i have a table with below field

• Id
• CompanyId
• Code
• Name

i want set Code column to unique , per CompanyId

回答1:

In your EntityTypeConfiguration you can do something like this:

Property(m => m.CompanyId)
    .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_YourUniqueIndexName", 1) { IsUnique = true }));
Property(m => m.Code)
    .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_YourUniqueIndexName", 2) { IsUnique = true }));

This will create a unique index on those 2 columns.

Make sure you use the same name for the unique index. Both need to be name "IX_YourUniqueIndex". If one is called "IX_Index1" and the other "IX_Index2" then it will create a unique index on each, which is not what you want

来源：https://stackoverflow.com/questions/31130642/how-can-create-unique-constraint-with-multi-column-with-entityframework