How to access data in a ViewModel of a UserControl from MainWindow

Question

I have a UserControl (MVVM pattern) and a MainWindow. The UserControl Model get all Data and hold it, now i want to access this data from the MainWindow and bind it to a Control.

But how?

EDIT

UserControl.cs:

public UserControl()
{
    InitializeComponent();
    DataContext = new ViewModel.UserControlViewModel(
                       new Model.UserControlModel(this.facade));
}

the ViewModel.cs (from UserControl.cs)

public string Status
{
    get { return _model.Status; }
    set
    {
        if (value == _model.Status)
        {
            return;
        }
            _model.Status = value;
            base.NotifyPropertyChanged();
        }
    }

MainWindow.xaml

<StatusBarItem Grid.Column="1">
    <TextBlock x:Name="txtStatus" Text="{Binding Path=???,
                                    Mode=TwoWay,
                                    UpdateSourceTrigger=PropertyChanged}" />
</StatusBarItem>

So it's not so easy (maybe only for me ;) ) to set the DataContext for this

If your mainwindow hold the instance of UserControl, then you access all the members of ViewModel using DataContext property. If possible, put the requirements more clearly. — Jawahar, Jul 30 '14 at 09:41
The Data should be only updated by the UserControl, so i need to access this one instance of the ViewModel in the MainWindow. And this means, i couldn't set the DataContext in the MainView. — benba, Jul 30 '14 at 10:14
While I accept that the 'duplicate' question is *not* an exact duplicate, it *does* provide a good solution for you to pass your data using `delegate`s, which are kind of like custom events, but far more versatile. Furthermore, it also links to another question with another example of using `delegate`s. You can use `delegate`s to pass data to and from children and parents of any kind. — Sheridan, Jul 30 '14 at 10:15

score 0 · Accepted Answer · answered Jul 30 '14 at 09:42

You could create a MainWindowViewModel which holds the data like so:

public class MainWindowViewModel {
    public AllDataType AllData {get;set;}
}

Now you bind the MainWindows DataContext to this ViewModel and access the data:

<MainWindow>
    <ctrl:UserControl DataContext="{Binding AllData}"/>
    <AnotherControl DataContext="{Binding AllData}"/>
</MainWindow>

How to access data in a ViewModel of a UserControl from MainWindow

1 Answers1