Is there an option to make Entity Framework revert empty strings to null?

Question

Hi

I am using an ADO.NET Entity-Framework ObjectContext to access my data store.

I want the if values are set with empty strings, they should automatically become null.

Answer 1

Not that I'm aware of.

You could possibly write a class that inherited from ObjectContext and override SaveChanges() to do that and use that instead of ObjectContext in your x.objectlayer.cs / x.designer.cs

Answer 2

I added this to the ObjectContext partial class. It does work, if you have better ideas, please post!

partial class MyObjectContext
{
    partial void OnContextCreated()
    {
        this.SavingChanges += new EventHandler(Entities_SavingChanges);
    }

    void Entities_SavingChanges(object sender, EventArgs e)
    {
        foreach (EntityObject entity in ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified).Select(entry => entry.Entity))
        {
            if (entity == null || entity is User) continue;

            string str = typeof(string).Name;

            var props = entity.GetType().GetProperties();

            var properties = from p in entity.GetType().GetProperties()
                             where
                             p.PropertyType.Name == str &&
                             p.IsDefined(typeof(EdmScalarPropertyAttribute), false) &&
                             p.IsDefined(typeof(DataMemberAttribute), false)
                             select p;

            foreach (var item in properties)
            {
                string value = (string)item.GetValue(entity, null);
                if (value != null && value.Trim().Length == 0)
                    entity.GetType().GetField("_" + item.Name, System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).SetValue(entity, null);
            }
        }
    }
}