Intercept model initialization

[r-work]

Is it possible to do some model initialization when:

1. Model is instantiated but before data is written to it.
2. After data is being written to it.

A small example would be something like the following:

public class MyModel
{
   public ObservableCollection<Item> Items { get; set; }

   public void OnModelCreating()
   {
       this.Items.IsLoading = true;
   }

   public void OnModelCreated()
   {
       this.Items.IsLoading = false;
   }
}

[ajcvickers]

@r-work Can you provide some more details on how this would be useful?

[r-work]

@ajcvickers this would be similar to EntityLoading and EntityLoaded which is mentioned here, however that issue is about 7 years old, so I presume that's not going to be implemented.

My use case is pretty much the same as what has been described in that issue (copy & paste):

EntityLoading:
After object instance is created but before its properties are initialized. Can be used to reset a flag that will be set in newly created instances but shouldn’t be set during initialization, i.e. for validation.

EntityLoaded:
Can be used to setup anything after an object has been materialized, i.e. event handlers, flags, etc.

[ajcvickers]

@r-work These are covered by #15911 and #10789.