Undrstanding the MVVM pattern

Question

Hello everyone.

I want to get some clarification about MVVM a possibly help me with a WPF app

I have this class, witch represent a User

   public int Id { get; set; }  
     
     
           private string _Name;  
           public string Name {  
               get { return _Name; }  
               set {  
                   if (_Name != value) {  
                       _Name = value;  
                       RaisePropertyChanged();  
                       Validate();  
                   }  
               }  
           }  
     
     
     
           private string _Email;  
           public string Email {  
               get { return _Email; }  
               set {  
                   if (_Email != value) {  
                       _Email = value;  
                       RaisePropertyChanged();  
                       Validate();  
                   }  
               }  
           }  
     
           private bool _isEnable;  
           public bool isEnable {  
               get { return _isEnable; }  
               set {  
                   if (_isEnable != value) {  
                       _isEnable = value;  
                       RaisePropertyChanged();  
                   }  
               }  
           }  
     
     
           private string _Address;  
           public string Address {  
               get { return _Address; }  
               set {  
                   if (_Address != value) {  
                       _Address = value;  
                       RaisePropertyChanged();  
                       Validate();  
                   }  
               }  
           }  
     
           private void Validate() {  
               if (string.IsNullOrEmpty(_Name) || string.IsNullOrEmpty(_Email) || string.IsNullOrEmpty(_Address)) {  
                   isEnable = false;  
               } else {  
                   isEnable = true;  
               }  
           }  
     
           public User() { }  
       }  
   }

That I use in a viewModel like

   public User User { get; set; }  
           public CloseDialogCommand CloseDialogCommand { get; set; }  
           public SaveCommand SaveCommand { get; set; }  
     
           public InputViewModel() {  
               User = new User();  
               SaveCommand = new SaveCommand(this);  
               CloseDialogCommand = new CloseDialogCommand(this);  
           }  
     
           public void Save(object user) {  
     
     
           }  
     
           internal void CloseDialog(Window window) {  
               window.Close();  
           }  
       }  
   }

And finally I se in my view

Ok my questions is, every documentation or youtube video that I see, they declare each string in the ViewModel and connect the ViewModel to the view (becouse all the properties are there and the the validation). What is te purpose of the Model then?, if I am respiting the same code I can put my validation in the model and that's it right?

My teacher, respond me this:

Instead of having the texbox binding to the User object, try creating independent string properties
In your XAML, use these string properties instead.

Now what I am doing in my app is disable the button, until the user fields everything, but the problem is that I have to press Tab on my keyboard so that the PropertyChange coud be fired

Answer

Model is the data layer and the business logic of the app or referred to as the domain object. It process data from ViewModel and infos the ViewModel if the data changes. You use RaisePropertyChanged() to info the ViewModel in your User class.
To enable the button with the three filed filled, you can set the implement it with triggers like below:

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Undrstanding the MVVM pattern

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