Is there an easy way to make EntityFramework use SQL default values?

Question

For example, most of my entities have DateCreated and DateModified fields. The defaults to these are set to GetUtcDate() in SQL Server.

If I try and create an entity and don't set these values, I get an exception saying it can't run the SQL insert because the date value is out of range. Makes sense because C# default dates are 1/1/0001 while SQL Server's minimum date is 1/1/1753.

So is there a way I can tell EF to either use the SQL Server default values, or to NOT try and insert columns which have not been set?

Answer 1

You must set StoreGeneratedPattern for those properties to Identity for DateCreated and Computed for DataModified. It is available in designer. Once you do that you cannot modify those values in your application - only database can set those properties. I wrote about this some article because this feature had bug before VS2010 SP1 but there are reports that it still doesn't work sometimes.

Answer 2

One solution is to override your generated entitycontext class by using partial. This will intercept inserts/updates on all the entity classes in your EF context:

public partial class MyEntities : ObjectContext
{
    public override int SaveChanges(SaveOptions options)
    {
        this.DetectChanges();

        foreach (var insert in this.ObjectStateManager.GetObjectStateEntries(System.Data.EntityState.Added))
        {
            if (insert.Entity.HasProperty("DateCreated"))
                insert.Entity.GetType().GetProperty("DateCreated").SetValue(insert.Entity, DateTime.UtcNow, null);
            if (insert.Entity.HasProperty("LastModified"))
                insert.Entity.GetType().GetProperty("LastModified").SetValue(insert.Entity, DateTime.UtcNow, null);
        }

        foreach (var update in this.ObjectStateManager.GetObjectStateEntries(System.Data.EntityState.Modified))
        {
            if (update.Entity.HasProperty("LastModified"))
                update.Entity.GetType().GetProperty("LastModified").SetValue(update.Entity, DateTime.UtcNow, null);
        }

        return base.SaveChanges(options);
    }
}

Or do something similar, looking for inserts/updates on your datestamp fields and removing them from the ObjectStateEntries collection?