MVVM - implementing 'IsDirty' functionality to a ModelView in order to save data

Question

Being new to WPF & MVVM I struggling with some basic functionality.

Let me first explain what I am after, and then attach some example code...

I have a scree

Answer 1

In my experience, if you implement IsDirty in your view model, you probably also want the view model to implement IEditableObject.

Assuming that your view model is the usual sort, implementing PropertyChanged and a private or protected OnPropertyChanged method that raises it, setting IsDirty is simple enough: you just set IsDirty in OnPropertyChanged if it isn't already true.

Your IsDirty setter should, if the property was false and is now true, call BeginEdit.

Your Save command should call EndEdit, which updates the data model and sets IsDirty to false.

Your Cancel command should call CancelEdit, which refreshes the view model from the data model and sets IsDirty to false.

The CanSave and CanCancel properties (assuming you're using a RelayCommand for these commands) just return the current value of IsDirty.

Note that since none of this functionality depends on the specific implementation of the view model, you can put it in an abstract base class. Derived classes don't have to implement any of the command-related properties or the IsDirty property; they just have to override BeginEdit, EndEdit, and CancelEdit.