in Entity framework, how to call a method on Entity before saving

Question

Below I have created a demo entity to demonstrate what I\'m looking for:

public class User :  IValidatableObject
{
    public string Name { get; set; }

             


        

Answer 1

I have an almost identical situation and I manage it by handling the SavingChanges event on the context.

First I create an interface that defines the timestamping operations:

public interface IHasTimeStamp
{
    void DoTimeStamp();
}

Then I implement this interface in my entities:

Public class User : IHasTimeStamp
(
    public void DoTimeStamp()
    {
        if(dataContext.Entry<User>(this).State == System.Data.EntityState.Added)        
        {            
            //add creation date_time            
            this.CreationDate=DateTime.Now;            
        }        

        if(dataContext.Entry<User>(this).State == System.Data.EntityState.Modified)        
        {            
            //update Updation time            
            this.UpdatedOnDate=DateTime.Now;        
        }
    }
}

The final step is to register the SavingChanges handler and implement it.

public partial class MyEntities
{
    partial void OnContextCreated()
    {
        // Register the handler for the SavingChanges event.
        this.SavingChanges
            += new EventHandler(context_SavingChanges);
    }

    // SavingChanges event handler.
    private static void context_SavingChanges(object sender, EventArgs e)
    {
        // Validate the state of each entity in the context
        // before SaveChanges can succeed.
        foreach (ObjectStateEntry entry in
            ((ObjectContext)sender).ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified))
        {
            if (!entry.IsRelationship && (entry.Entity is IHasTimeStamp))
            {
                (entry.Entity as IHasTimeStamp).DoTimeStamp();
            }
        }
    }
}