How do I upsert a record in ADO.NET EF 4.1?

Question

I\'m trying to accomplish something really simple and I can\'t find how to do it using Entity Framework 4.1.

I want a controller method that accepts an object and

Answer 1

I know this question is old and has an accepted answer, but I think there is a better solution: it doesn't require an extra interface to be implemented or key type to be defined.

public static class DbSetExtensions
{
    public static EntityEntry AddIfNotExists(this DbSet dbSet, TEnt entity, Func predicate) where TEnt : class
    {
        var exists = dbSet.Any(c => predicate(entity).Equals(predicate(c)));
        return exists
            ? null
            : dbSet.Add(entity);
    }

    public static void AddRangeIfNotExists(this DbSet dbSet, IEnumerable entities, Func predicate) where TEnt : class
    {
        var entitiesExist = from ent in dbSet
            where entities.Any(add => predicate(ent).Equals(predicate(add)))
            select ent;

        dbSet.AddRange(entities.Except(entitiesExist));
    }
}

So later it can be used like this:

using (var context = new MyDbContext())
{
    var user1 = new User { Name = "Peter", Age = 32 };
    context.Users.AddIfNotExists(user1, u => u.Name);

    var user2 = new User { Name = "Joe", Age = 25 };
    context.Users.AddIfNotExists(user2, u => u.Age);

    // Adds user1 if there is no user with name "Peter"
    // Adds user2 if there is no user with age 25
    context.SaveChanges();
}