WPF MVVM Implementation 

There are even cases where you're not able to change the model yourself at all, e.g. when using 3rd party objects. Only the view model is always under your complete control.

i know it's kinda off topic but does anybody know of a good place to watch newly released tv shows online?

@Xander Alijah i would suggest FlixZone. You can find it by googling :)

@Cannon Toby definitely, I have been using flixzone for since april myself :)

@Cannon Toby thank you, I went there and it seems like they got a lot of movies there :D I appreciate it!

@Xander Alijah You are welcome :D

Hi EL, i'm trying to add one text box and bind it with name of selected items in the list view. But, unable to do it. Could you try it and let me know how to do it.

You are correct, this tutorial is wrong.

do it this way, private Person _person = new Person();

You are right.. Coming to yr first query.. What happens if we need to change the model, hence we keep our models or entities seperate and implement it's collection in viewModel.. The approach you thought was also correct but MVVM approaches differ across developers. This is the reason why microsoft has not released any stable template of MVVM in visual studio.. Only toolkits like MVVM light exists from third party. My approach was simple to make everyone understand.. Great point though....

same here

Pls mail me yr id at mailid shown on video..

u have not mention ur mail id in video...cant find it.....plz give it here.......can u plz send me the project on vivekbsnl30@gmail.com

I am also getting a NullRefrenceException in the If logic in CanSubmitExecute in the PersonViewModel. i have also Instantiated the PersonViewModel via constructor

Just add the constructor in PersonViewModel class which initalizes the field _person which is of type Person and _persons which of type ObservableCollection. public PersonViewModel() { this._person=new Person(); this._persons=new ObservableCollection();}

IDataError Info interface if you are working with MVVM

Yes , view knows viewmodel and viewmodel knows model. There is direct connection between view and model. But we are using viewmodel to connect both . In xaml we have defined binding contect(source) as view model. so from the view model we can able to access the model and its properties. Hence we can able to get person properties in xaml(view) I hope it's helpful

object _person and _persons are not properly initialized in ModelView Class. use to following to update code private Person _person = new Person(); and private ObservableCollection _persons = new ObservableCollection();

@@TheBhai420 Thank you, this solved it for me!

@@TheBhai420 thank you this solved my problem..

ravi joshi by passing parent viewmodel's reference to chid view model. Untill you are passing data between window's vm. 2) you can use event bus. Or 3) singleton will do the work for you 4) best of all use reactive programming

@@keshavejat Hi, could you help me to add one more text box in the same code which tells the first name of the selected item in the list view.

Build separate logic for command action, and hook up in the same way you did for first button.. Try it, will happy to help if u dnt succeed

Valid question, but the sole purpose of MVVM is to achieve decoupling. Now when we implement this interface the change notification is sent as an event which gives us decoupling. There is also a way to implement in view model that is done by MVVM purists. But problem with that approach is VM is the class where we have our business logic and implementing change notification event could violate Single responsibility principle. Hence generally change notification is implemented through Model in general practice.

You should not implement it on your Model but only on your ViewModel, and then VM will talk with your model, and VM you have already bound to main application.

I had a same problem like you. For a short moment on 21:06 you can see the definition private ICommand _SubmitCommand; He made a change during a visible cut in the video but unfortunately he did not mention that. I hope this helps! :)

using System; using System.Collections.Generic; using System.Collections.ObjectModel; using System.ComponentModel; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Input; using _21V_WPF_MVVM.Command; using _21V_WPF_MVVM.Model; namespace _21V_WPF_MVVM.ViewModel { public class PersonViewModel : INotifyPropertyChanged { private Person _person; public Person Person { get { return _person; } set { _person = value; NotifyPropertyChanged("Person"); } } public PersonViewModel() { Person = new Person(); PersonS = new ObservableCollection(); } private ObservableCollection _PersonS; public ObservableCollection PersonS { get { return _PersonS; } set { _PersonS = value; NotifyPropertyChanged("PersonS"); } } private ICommand _SubmitCommand; public ICommand SubmitCommand { get { if (_SubmitCommand == null) { _SubmitCommand = new RelayCommand(SubmitExecute, CanSubmitExecute, false); } return _SubmitCommand; } } private void SubmitExecute(object parameter) { PersonS.Add(Person); } private bool CanSubmitExecute(object parameter) { if (string.IsNullOrEmpty(Person.FName) || string.IsNullOrEmpty(Person.LName)) { return false; } else { return true; } } public event PropertyChangedEventHandler PropertyChanged; protected void NotifyPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } } }

hi dude, u must define it : private ICommand _SubmitCommand; then : public ICommand SubmitCommand { … }

in PersonViewModel class

I an getting the same error. Did you get the answer?

oh . I just realize I never initialize person = new Person();

​Hey @@joshuasafabre1202 where did you initialize it??/ even i am getting the same error

​@@sandeeppuvvadi1729 Hi, could you help me to add one more text box in the same code which tells the first name of the selected item in the list view.

In the same exact moment he pasted two methods, named SubmitExecute(object parameter) and CanSubmitExecute(object parameter) below the SubmitCommand property.

@@deadlock107 thank you

Thank you so much, this helped us soooooo much. Thank you

@@meghnatiwari2527 You're welcome :)

Hi, could you help me to add one more text box in the same code which tells the first name of the selected item in the list view.