In a Xamarin project, the ViewModel is in between a view and the corresponding data model to exchange required information. If any change is required in the code, select the appropriate ViewModel class file as displayed in the following figure:
Changes to the ViewModel are typically made when you need to add:
New controls to the View
Special processing for specific controls (For example, more validation or data transformation)
Custom business logic to manipulate the data from the view, before it is sent to the Data Model