Generic Insert or Update for Entity Framework

Question

Say I have an insert method:

public T Add(T t)
{
   context.Set().Add(t);
   context.SaveChanges();
   return t;
}

And a

Answer 1

You could use an interface and do something like this. I used an explicit implementation so the rest of your code does not have to deal with it.

// I am not 100% sold on my chosen name for the interface, if you like this idea change it to something more suitable
public interface IIsPersisted {
    bool IsPersistedEntity{get;}
    int Key {get;}
}

public class SomeEntityModel : IIsPersisted{
    public int SomeEntityModelId {get;set;}

    /*some other properties*/

    bool IIsPersisted.IsPersistedEntity{get { return this.SomeEntityModelId > 0;}}
    int IIsPersisted.Key {get{return this.SomeEntityModelId;}}
}



public T UpdateOrCreate(T updated) where T : class, IIsPersisted
{
    if (updated == null)
        return null;

    if(updated.IsPersistedEntity)
    {
        T existing = _context.Set().Find(updated.Key);
        if (existing != null)
        {
            context.Entry(existing).CurrentValues.SetValues(updated);
            context.SaveChanges();
        }
        return existing;
    }
    else
    {
        context.Set().Add(updated);
        context.SaveChanges();
        return updated;
    }
}

Edit

I just now saw this:

is there a more efficient way that avoids a round trip to the database than using context.Set().Find(key)

If you want the whole entity updated from a detached state then the easiest thing to do is this.

context.Entry(updated).State = EntityState.Modified;
context.SaveChanges();

This will mark the whole entity as dirty and save everything back to the database.