Unique columns values in Entity Framework - Code First

Question

I have an entity like this:

public class User
{
    public string Name { get; set; }
    public string LastName { get; set; }
    public string Username { get; set; }   // this is an EmailAddress

    [Key]
    public Guid Id { get; set; }      
}

How can I define the Username to be unique too?

Using Entity Framework 6.1.3

Community · Accepted Answer · 2017-05-23 11:45:46Z

3

If you’re using the newest EF (6.1+) then you can use this code:

[Index("UserNameIndex", IsUnique = true)]
[MaxLength(100)]
 public string UserName { get; set; }

With EF of earlier versions there’s more complex approach which you can check here: Unique key with EF code first

edited May 23, 2017 at 11:45

CommunityBot

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answered Jun 4, 2016 at 22:00

Ivan Yurchenko

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4 Comments

Felix D. Over a year ago

ty will try that immediately :D

Felix D. Over a year ago

I am getting this exception: "Column 'Username' in table 'dbo.Users' is of a type that is invalid for use as a key column in an index."

Felix D. Over a year ago

it seems to correspond to stackoverflow.com/a/23055838/4610605 can you help me out ? I don't get whats wrong ....

Ivan Yurchenko Over a year ago

Try to add the MaxLength attribute. The Indexes length is limited so you have to specify the max length value for your property.

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