Question

Say I have ViewModel class MyViewModel like:

  public class MyViewModel : ViewModelBase
  {
   private Person _person;
        public Person Person
        {
            get { return _person; }
            set
            {
                if (this._person != value)
                {
                    this._person = value;
                    this.RaisePropertyChanged("Person");
                }
            }
        }

   private AddNew(){
      this =  new MyViewMode(new Person());
   }
  }

What I want is try to create new instance inside this view mode in method AddNew().
When this VM bind to UI, I want to user can to change the viewmodel for new entity without change UI.

But I can’t do that because code this = new MyViewMode(new Person()); won’t work.

How to resolve this problem?

Answer 1

I would recommend not to do something like this…
Google for view-first or viewmodel first…
This is an ongoing discussion with lot’s of opinions which realy makes sense.

http://wildermuth.com/2009/05/22/Which_came_first_the_View_or_the_Model

Further more I would look into the pattern of the ServiceLocator.
Basicaly a service which creates the viewmodels for you…

http://johnpapa.net/silverlight/simple-viewmodel-locator-for-mvvm-the-patients-have-left-the-asylum/
http://csharperimage.jeremylikness.com/2010/03/viewmodel-binding-with-managed.html