Validating against a duplicate entry in ASP.NET 5 MVC 6
asp.net-core asp.net-core-mvc entity-framework-core
Question
Using asp.net 5, MVC 6, code first, entity Framework 7, beta 8.
I understand that some validation can be handled through annotations on properties, e.g. Data Type, min, max values and the jquery scripts, but I'm not sure how in code validation against a duplicate entry getting into the database, like preventing a duplicate e-mail reg on a form.
Is there any annotation that I can use for this on my model property or do I need to code something in my controller to handle this custom validation? Anyone got an example to share?
Popular Answer
EF7 does not have any magic to prevent duplicate values in a table. The only way to validate duplicates is to make a roundtrip to the database. The best way to do this is with a unique constraint. This may be expressed as a unique index. Any attempt to insert a duplicate entry should throw an exception.
That said, you can configure EF7 to recognize the unique index in your database in your OnConfiguring method. See Indexes : Configuring Your Model in the EF7 docs.
modelBuilder.Entity<User>()
.Index(b => b.Email)
.Unique();