Question

I have a WPF DataGrid bound to some entities (Entity Framework 4+).

User then edits the DataGrid and presses SAVE. Data is then saved back to MS SQL Server 2008 using SaveChanges(). Well… now, I would like to have AUTOMATIC timestamp which stores the time of the last change and updates itself automatically.

Guys, is it possible? How?

Thank you, James

Answer 1

The easiest solution to achieve this is on the database level:

• Create a new column in the table for storing your DateTime value.
• Create database trigger to set the column for each insert or update to the table.
• Map the new column as property in your entity
• Set StoreGeneratedPattern for the new property to Computed so the value generated in the database is correctly updated to your attached entity after each insert or update.

If you don’t like the trigger you must do it manually in overriden SaveChanges where you find all entities which will be inserted or updated and set the column:

public override int SaveChanges(SaveOptions options)
{
    var entities = ObjectStateManger.GetObjectStateEntries(EntityState.Added | EntityState.Modified)
                                    .Select(e => e.Entity)
                                    .OfType<YourEntityType>();

    DateTime now = DateTime.Now;
    foreach(var entity in entities)
    {
        entity.Updated = now;
    }

    return base.SaveChanges(options);
}