Question

Based on this link it looks like I can get date inserted / date modified information “for free” (without the need for triggers etc.) using Sql Server 2008 by simply enabling Change Tracking. I am using Entity Framework to access the data. My question is, how do I access date modified / date inserted information for the database records via Entity Framework and LINQ?
I’m using VS2008 so I don’t have the new EF v4 stuff yet (but if it can be done in the new EF please let me know).
Thanks.

Answer 1

OK, this works beautifully (also see this article)…

public partial class MyEntities
{
    partial void OnContextCreated()
    {
        this.SavingChanges += new System.EventHandler(CustomSavingChangesLogic);
    }

    /// <summary>
    /// Apply timestamps
    /// </summary>
    public void CustomSavingChangesLogic(object sender, System.EventArgs e)
    {
        var changedEntities = ((ObjectContext)sender).ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified);
        foreach (var stateEntryEntity in changedEntities)
        {
            if(!stateEntryEntity.IsRelationship) {
                var entity = stateEntryEntity.Entity;
                var lastModifiedPropInfo = entity.GetType().GetProperty("LastModified");
                if (lastModifiedPropInfo != null)
                    lastModifiedPropInfo.SetValue(entity, DateTime.UtcNow, null);
                if (stateEntryEntity.State == EntityState.Added)
                {
                    var createdPropInfo = entity.GetType().GetProperty("Created");
                    if (createdPropInfo != null)
                        createdPropInfo.SetValue(entity, DateTime.UtcNow, null);
                }

            }
        }
    } 

}