[Solved] How to use short-living context?

[Froggie]

Hi!
I want to use short-living contexts, but I'm not able to achieve the saving of changed objects.
Can you help me?

This is my current code:

internal void RefreshView()
   {
            List<CustomModel> availableCustomModels;
            using (var dbContext = new Context())
            {
                availableCustomModels = dbContext.CustomModels.ToList();
            }

            viewController.RefreshView(availableCustomModels);
        }

 private void viewController_Save(object sender, CustomModelEventArgs<CustomModel> e)
        {
            using (var dbContext = new Context())
            {
                var modelToSave = (from x in dbContext.CustomModels
                                  where x.Id.Equals(e.Model.Id)
                                  select x).FirstOrDefault();

                //TODO implement saving the changes
                if (modelToSave != null)
                {
                    dbContext.SaveChanges();
                }
            }

            RefreshView();
        }

private void viewController_Delete(object sender, CustomModelEventArgs<CustomModel> e)
        {
            using (var dbContext = new Context())
            {
                var modelToDelete = (from x in dbContext.CustomModels
                                    where x.Id.Equals(e.Model.Id)
                                    select x).FirstOrDefault();

                if (modelToDelete != null)
                {
                    dbContext.Delete(modelToDelete);
                    dbContext.SaveChanges();
                }
            }

            RefreshView();
        }

[Boyan]

Hi Sebastian,

As I reviewed your code I noticed that you could manually synchronize the properties of modelToSave with the corresponding values coming from the event parameter e.Model and thus updating the entity, like that:

private void viewController_Save(object sender, CustomModelEventArgs<CustomModel> e)
{
    using (var dbContext = new Context())
    {
        var modelToSave = (from x in dbContext.CustomModels
                          where x.Id.Equals(e.Model.Id)
                          select x).FirstOrDefault();

        //TODO implement saving the changes
        if (modelToSave != null)
        {
            modelToSave.Id = e.Model.Id;
            // ...
            // The rest of the properties
            // ...
            dbContext.SaveChanges();
        }
    }

    RefreshView();
}

As an alternative approach you could choose to work with attached/detached copies of your entities. This would allow you to avoid manual synchronization in your code.  For example:

private void viewController_Save(object sender, CustomModelEventArgs<CustomModel> e)
{
    if(e.Model != null
    {
        using (var dbContext = new Context())
        {
            dbContext.AttachCopy(e.Model);
            dbContext.SaveChanges();
        }

        RefreshView();
    }
}

For your convenience I have prepared a small sample project fully demonstrating the later approach. Please find it attached.

Additionally I would recommend you going through our sample kit containing a number of applications involving various technologies and application structures.

Should you have any further questions please let us know. 

Regards,
Boyan
Telerik