EF Code First Fluent API define unique constraint

Question

Im trying to enforce unique constraint of a column using fluent configuration for code first. Is there any better way than implementing it in business logic or using something like below

context.ObjectContext.ExecuteStoreCommand("CREATE UNIQUE CONSTRAINT...");

Or I was wondering if it's not possible to implement unique constrain using fluent configurations?

EDIT :

It's confirmed that this is not possible with fluent configurations. But then again I'm wondering what's the best way to do this? And would like to know the reason behind EF not supporting this.

The team is considering: http://entityframework.codeplex.com/workitem/299 — ErikEJ, Mar 19 '13 at 17:59

score 2 · Answer 1 · answered Jul 05 '13 at 09:28

2

In this example you can see how to define a Unique key attribute and use it in any Entity.

http://code.msdn.microsoft.com/windowsdesktop/CSASPNETUniqueConstraintInE-d357224a

answered Jul 05 '13 at 09:28

Imran Rashid

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1

Thanks for the reply Imran. Actually it's a good way to do it. But in the end what it does is executing a vendor specific SQL statement, so in case I change my database to a different vendor I will end up modifying the code. But I do agree I will have to modify only one place. – Geethanga Jul 13 '13 at 05:42

score 1 · Accepted Answer · answered Mar 18 '13 at 13:12

1

I have this problem occurred before

it can not implement unique constrain using fluent API。

so, the way you used is correct!

answered Mar 18 '13 at 13:12

czclk

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thanks for the reply. But if I do it using a command it will be dependent of my database implementation. That's something I don't want to have. – Geethanga Mar 19 '13 at 14:03

score 1 · Answer 3 · answered Feb 13 '14 at 19:16

1

This is possible with DbMigrations...

public override void Up()
{
    CreateIndex("dbo.MyTableName", "MyColumnName", unique: true); 
}

answered Feb 13 '14 at 19:16

Ben Ripley

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Yes indeed, I also have written a blog post on that you can find it here (http://goo.gl/Ks9HZI). But my original question was if there's a way to do it with Fluent API. – Geethanga Feb 15 '14 at 05:06
The problem with putting custom code into migrations is that you risk losing that code when you decide to purge/combine/regenerate your migrations. I suggest keeping all your configurations in the `EntityTypeConfiguration` classes. Check my answer on how to it: http://stackoverflow.com/a/25779397/111438. – niaher Sep 11 '14 at 05:02

score 1 · Answer 4 · edited May 23 '17 at 12:23

It can be done with a custom extension method:

using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.Infrastructure.Annotations;
using System.Data.Entity.ModelConfiguration.Configuration;

internal static class TypeConfigurationExtensions
{
    public static PrimitivePropertyConfiguration HasUniqueIndexAnnotation(
        this PrimitivePropertyConfiguration property, 
        string indexName,
        int columnOrder = 0)
    {
        var indexAttribute = new IndexAttribute(indexName, columnOrder) { IsUnique = true };
        var indexAnnotation = new IndexAnnotation(indexAttribute);

        return property.HasColumnAnnotation("Index", indexAnnotation);
    }
}

Check the full answer here: https://stackoverflow.com/a/25779348/111438

EF Code First Fluent API define unique constraint

4 Answers4