EF Code-First Add Unique Index to Column

Question

In my Entity-Framework Code-First Model I have a Table that needs one column to have unique values. I want to apply an Unique Index to it as I saw that it is very easy in EF 6.1

public partial class User
{
   public int Id { get; set; }

   [Index(IsUnique = true)]
   public virtual SharePoint SharePoint { get; set; }
}

When creating a migration for this code the following is being generated:

public override void Up()
{
    CreateTable(
        "dbo.Users",
        c => new
            {
                Id = c.Int(nullable: false, identity: true),
                SharePoint_Id = c.Int(nullable: false),
            })
        .PrimaryKey(t => t.Id)
        .ForeignKey("dbo.SharePoints", t => t.SharePoint_Id)
        .Index(t => t.SharePoint_Id);
}

As you can see, the Index is not Unique here.

Also the DB Indices tell that the created index is not unique

None Unique SQL Index

I saw in older versions of EF that you had to do this via the Model Builder, which I tried aswell:

modelBuilder.Entity<Configuration>()
    .Property(p => p.SharePoint)
    .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute() { IsUnique = true }));

Which sadly results in the error:

The type 'kData.Sharepoint' must be a non-nullable value type in order to use it as parameter 'T' in the generic type or method 'System.Data.Entity.ModelConfiguration.Configuration.StructuralTypeConfiguration.Property (System.Linq.Expressions.Expression>)

So how is it possible to create a code-first migration, adding an Unique Index to a Column in EF 6.1?

Maybe these SO topics could be helpful? http://stackoverflow.com/questions/2230657/help-with-c-sharp-generics-error-the-type-t-must-be-a-non-nullable-value-ty http://stackoverflow.com/questions/16730753/the-type-t-must-be-a-non-nullable-value-type-in-order-to-use-it-as-parameter — Prokurors, Apr 23 '15 at 13:19
@Prokurors these only describe the Error Message. The Field `SharePoint` is **not** specified as nullable as you can see in the declaration of the Table. I think something else, maybe EF internally, is wrong here — Vinz, Apr 23 '15 at 13:33

score 0 · Answer 1 · answered Apr 23 '15 at 13:20

0

Probably this is because you are specifying Unique constraint on navigation property that does not exist in the database rather it's foreign key is there on database so you may try applying attribute to foreign key SharePoint_Id and make it not nullable and then it should work.

modelBuilder.Entity<User>()
.Property(p => p.SharePoint_Id)
.HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute() { IsUnique = true }));

answered Apr 23 '15 at 13:20

Jenish Rabadiya

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Thanks for the answer. I used to make a SharePoint an Object and virtual as it exists in another table (is a foreign key to it). So the `SharePoint_Id` will be accessed by EF internally and it will load the whole Object from my other Table instead of giving me an ID here, I think. I cannot specify `SharePoint_Id`. Its not available in my EF C# Model :( – Vinz Apr 23 '15 at 13:30
@Vinzenz you can specify foreign key name. There is `ForeignKeyAttribute` attribute defined in DataAnnotation lib for such a use or you can have `HasForeignKey` method in case you are using fluent api. – Jenish Rabadiya Apr 23 '15 at 13:35
I was afraid that I had to do it that way... Sad that Entity Framework has no functionalities yet, to detect such scenarios – Vinz Apr 23 '15 at 13:44

EF Code-First Add Unique Index to Column

1 Answers1