StoreGeneratedPattern - Is this supported?

In one of our EF4 based projects we just hit the old 'StoreGeneratedPattern' bug in VS2010, where it doesn't correctly set the attribute in the SSDL area for columns that have a 'Default Value or Binding' set.
However, the EF4 fix/bodge of adding 'StoreGeneratedPattern=Computed' doesn't cut the mustard; the purpose of this field is to specify what should be inserted in this field if no value has been provided.

Ideally we need a new enum in the EF4 set; StoreGeneratedPattern.DefaultValue or something.

So I decided to try the same thing in DF2010...

As an example, I have a table with three columns:
Name        nvarchar(50)
LastEdited  DateTime (Default = GetDate())
ts          TimeStamp

Now when I generate the edmx, it sets ts to StoreGeneratedPattern=Computed, but ignores LastEdited.
However, a simple creation of this entity, set the name, AddEntity, then call SaveChanges complains (unlike EF4) that 'ts' must be supplied. Of course I can supply with with a dummy array of byte[8] which is ignored...

I'm sure I can bodge up the underlying entity through partial classes and property interceptors, but I'm sure this is not the intended method of reflecting the database structure. I was hoping DF would help with the second issue I mention, but we appear to have tripped at the first!

Yes, as you noticed:

A temporary (but slightly dodgy) workaroundfor the TimeStamp properties is as follows.
However, I can't see any way of accessing the fact it is specifically a TimeStamp field (this example is assuming all Byte[] fields are timestamps), and it doesn't even touch on the Default problem above.
I could have used the field name "ts" for all timestamps, but the ideal would be to know the underlying database type.

    public class QsEntitySaveInterceptor : EntityServerSaveInterceptor
    {
        protected override bool ValidateSave()
        {
            var now = DateTime.Now;
            var e = base.EntityManager.FindEntities(EntityState.Added).Cast<Entity>().ToList();
            foreach(var entity in e)
            {
                var timestamps = (entity).EntityAspect.EntityMetadata.EntityProperties.Where(ep => ep.DataType == typeof(byte[]));
                foreach (var prop in timestamps)
                    prop.PropertyInfo.SetValue(entity, new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }, null);
                var createddates = (entity).EntityAspect.EntityMetadata.EntityProperties.Where(ep => ep.Name == "DateCreated" || ep.Name == "LastUpdated");
                foreach (var prop in createddates)
                    prop.PropertyInfo.SetValue(entity, now, null);
            }
            return base.ValidateSave();
        }
    }

So... interesting questions:

• is there any way to find the database type that underlies an Entity property?
• is it right that DateTime fields on new Entities are always set to Today? This might be dangerous; forgetting to set it in code might not be detected, and what if we want to know in the Save Interceptor whether a value was entered or not? Might a date of DateTime.Min (or 01-01-1900 for non-DateTime2) not be better?
  Also, non-nullable string fields don't have a default of String.Empty, so why are DateTimes set to a value?
  
• do you know of any way to make the EF4 designer retrieve other SQL metadata such as 'Default Value or Binding'?
• is it possible to influence the SQL of fields that will be inserted on added entities (i.e. remove inserted parameters so defaults are used)?

Ah, so many questions and so little time to answer them all...



Edited by jsobell - 24-Jun-2010 at 6:09pm