C# WPF & MVVM | update data of a property with a binding to the object

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C#

WPF

MVVM

PRISM

Hi guys,

This is actually my first question here. I tend to find all the answers browsing the net, but haven't found the answer to that question yet...

*I've created this code especially for the question, look below please!*

I've been trying to figure out if there is any way to do something as follows:
1) I have a view model base with IPropertyChanged
2) I have a model for example a student model with 2 properties - ID and Name.
3) I have a simple MainWindow view, which is set on MainWindowViewModel datacontext.
4) The view shows a datagrid bounded to "Students" from MainWindowViewModel which is an OC of students - ObservableCollection<student>(with random data I inserted).
5) I've configured the datagrid to have SelectedItem = {Binding SelectedStudent}
6) I have set 2 text boxes to the SelectedStudent.ID and SelectedStudent.Name, and the values show up nicely whenever I select a student.
7) I also see the changes in the textbox's text in the UI, but not in code(!!!)
* I've set UpdateSourceTrigger=OnPropertyChanged, and binding Mode=TwoWay

The problem starts whenever I want to try to EDIT the properties values by changing the current value shown in the text boxes.
Maybe I don't understand what I'm doing while I bind this way, but I put a debug breakpoint on the "get/set" of my properties - ID and Name, and nothing seems to invoke the "Set" method(On the SelectedStudent - maybe that's part of my problem?).

This works if i work hard and create 2 new properties like "Id", and "Name" under the view model and bind them to the textboxes instead... I could change their value and the "set" would invoke i could see it on the breakpoint in the properties themselves - the problem starts only when I try to change my OBJECT's child properties...

Do I need to set the stackpanel "local" datacontext(for example) to something else???

Just to let you know, I'm working with PRISM, but I want to make this as simple as possible(if you know the answer in PRISM I would love to know!).


Thanks a lot to everyone who tries to help!

-----------------
CODE(Everything is here!):
-----
ViewModelBase:

public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged([CallerMemberName]string caller = null)
    {
        var handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(caller));
        }
    }
}

----------------
MainWindowViewModel:

public class MainWindowViewModel : ViewModelBase
    {
        private ObservableCollection<Student> _students;
        private Student _selectedStudent = null;

        public Student SelectedStudent
        {
            get { return _selectedStudent; }
            set 
            {
                _selectedStudent = value;
                OnPropertyChanged();
            }
        }

        public ObservableCollection<Student> Students
        {
            get { return _students; }
            set
            {
                _students = value;
                OnPropertyChanged();
            }
        }

        public MainWindowViewModel()
        {
            Students = new ObservableCollection<Student>();
            Students.Add(new Student { Id = "0", Name = "Jackson" });
            Students.Add(new Student { Id = "1", Name = "Jenny" });
        }
    }

-----------------
Student:

public class Student : ViewModelBase
{
    private string _id;
    private string _name;

    public string Id
    {
        get { return _id; }
        set { _id = value; OnPropertyChanged(); }
    }

    public string Name
    {
        get { return _name; }
        set { _name = value; OnPropertyChanged(); }
    }

}

-------------------
MainWindow.xaml:

<Window.DataContext>
    <local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <StackPanel Grid.Row="0">
        <TextBlock Text="Name: "/>
        <TextBox Text="{Binding SelectedStudent.Name, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>
        <TextBlock Text="Id: "/>
        <TextBox Text="{Binding SelectedStudent.Id, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>
    </StackPanel>

    <DataGrid Grid.Row="1" x:Name="dgStudents" ItemsSource="{Binding Students, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" SelectedItem="{Binding SelectedStudent, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" AutoGenerateColumns="True"/>
</Grid>

What I have tried:

Everything I possibly could, many things I saw on the net... Tried going over binding guides but all they showed are mostly things I know.. I haven't found this specific editing case that I'm trying to do - pretty surprising...