How can I automatically set a DateUpdated column using the Entity Framework?

Question

I have a bunch of tables that have DateUpdated columns.

How can I have those fields automatically set to DateTime.Now when the objects are persisted back to the data store when SaveChanges() is called.

I don't need to do it across the board with one piece of code. I would be OK with adding event handlers in all of the partial classes, but I didn't see anything I could hook into. And I'd rather keep it in the code, rather than adding triggers to the database.

Here are my ideas:

I think I could do some crazy reflection automagic on the ObjectContext.SavingChanges event, but I don't think that is the best solution.

Or, I could add an interface that contains a DateUpdated property, and implement it with all the classes that have that field. Then use ObjectContext.SavingChanges event to set the property on all of the changed objects that implement that interface.

Any ideas?

Thanks in advance!

Dave Swersky · Accepted Answer · 2009-08-21 01:18:12Z

3

This is one of those exceedingly rare cases where I think database triggers actually have some utility. Normally I dislike them strongly... they have a habit of hiding business logic in the darkest corner of a system. However, for something as simple as a Last Modified Date, I think they may be the simplest, most scalable, and best performing solution overall.

answered Aug 21, 2009 at 1:18

Dave Swersky

34.8k9 gold badges83 silver badges120 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jacob Proffitt · Accepted Answer · 2009-08-20 22:09:57Z

0

Personally, I'd go with creating a custom object for my tables to inherit from. You can set the Base Type for your tables to this object and then play with it from there. This allows you to override OnPropertyChanged so that it will execute whenever any property is changed on the table. This is particularly useful if you can count on the convention that the field you're interested in is named "DateUpdated". It'd take some minor reflection magic, but not really much.

using System.Reflection;
public class TableBase : System.Data.Objects.DataClasses.EntityObject
{
    protected override void OnPropertyChanged(string property)
    {
        base.OnPropertyChanged(property);

        if (property != "DateUpdated")
        {
            PropertyInfo prop = this.GetType().GetProperty("DateUpdated");
            if (prop != null && prop.PropertyType.IsAssignableFrom(typeof(DateTime)))
            {
                prop.SetValue(this, DateTime.Now, null);
            }
        }
    }
}

Set the Base Type of your tables to TableBase and if they have a property of "DateUpdated" that property will become Datetime.Now as soon as any property is changed.

answered Aug 20, 2009 at 22:09

Jacob Proffitt

12.8k3 gold badges43 silver badges47 bronze badges

3 Comments

John B Over a year ago

Unfortunately, I think the "OnPropertyChanged" event fires every time the entity is changed, even when data is being loaded. So I think doing a select would cause the field to be updated in this case.

Jacob Proffitt Over a year ago

That's okay. Further experimentation reveals that Base Type is hard-wired to be table entities within the same model rendering it useless for this purpose. So much easier in Linq for SQL. <sigh>

ProfK Over a year ago

I realise this is very likely not the problem domain, but this solution is not available in EF Code First.

Collectives™ on Stack Overflow

How can I automatically set a DateUpdated column using the Entity Framework?

2 Answers 2

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related