C# - Entity framework, duplicate unique exception?

Question

Hello there, I'm trying to catch the exception throwen when I insert a already existing user with the given username into my database. As the title says then I'm using EF. The only exception thats throwen when I try to insert the user into to db is a "UpdateException" - How can I extract this exception to identify whether its a duplicate exception or something else?

Answer 1

catch (UpdateException ex)
{
    SqlException innerException = ex.InnerException as SqlException;
    if (innerException != null && innerException.Number == ??????)
    {
        // handle exception here..
    }
    else
    {
        throw;
    }
}

Put the correct number at ?????? that corresponds to unique constraint violation (I don't know it from the top of my head).