how to turn off (with a checkbox) WPF/MVVM DataGrid grouping that is implemented using CollectionViewSource?

Question

I have working implementation of datagrid grouping. Below is what i do (GroupStyle with expander omitted):

<CollectionViewSource x:Key="SelectedObjectsViewSource" Source="{Binding SelectedObjectItems}">
    <CollectionViewSource.GroupDescriptions>
       <PropertyGroupDescription PropertyName="TableId"/>
    </CollectionViewSource.GroupDescriptions>
</CollectionViewSource>


<DataGrid Name="SelectedObjectsGrid" 
     ItemsSource="{Binding Source={StaticResource SelectedObjectsViewSource}}"
     SelectionMode="Extended"
     CanUserAddRows="False"
     AutoGenerateColumns="False">

I would like to add a checkbox that user can turn off/on grouping. But i have no idea how to implement this in MVVM

Answer 1

I advise you to bind the checkbox to a bool property of the viewmodel where its setter also sets the grouping status of the collectionview following the assigned value. Like in the following sample: where the bool property bound to the checkbox status is GroupView and the collection bound to the datagrid is View.

C# ViewModel

class ViewModel : INotifyPropertyChanged {
    public event PropertyChangedEventHandler PropertyChanged;
    protected void NotifyPropertyChanged(string info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    private ICollectionView _View;
    public ICollectionView View
    {
        get
        {
            return _View;
        }
        set
        {
            _View = View;
            NotifyPropertyChanged("View");
        }
    }

    private bool _GroupView;
    public bool GroupView
    {
        get
        {
            return _GroupView;
        }
        set
        {
            if (value != _GroupView)
            {
                // Clear Grouping status of the view
                View.GroupDescriptions.Clear();
                if (value)
                {
                    // If true set Grouping status
                    View.GroupDescriptions.Add(new PropertyGroupDescription("TableId"));
                }
                _GroupView = value;
                NotifyPropertyChanged("GroupView");

                // Notify the UI that also the View changed in order to redraw the datagrid with or without grouping
                NotifyPropertyChanged("View");
            }
        }
    }   
}

C# Code Behind

public partial class MyWindow : Window
{
    public MyWindow()
    {
        InitializeComponent();
        ViewModel myViewModel = new ViewModel();
        myViewModel.View = .....;
        DataContext = myViewModel;

    }
}

XAML

<StackPanel>
    <CheckBox IsChecked="{Binding GroupView, Mode=TwoWay}"/>
    <DataGrid Name="SelectedObjectsGrid" 
            ItemsSource="{Binding View, Mode=TwoWay}"
            SelectionMode="Extended"
            CanUserAddRows="False"
            AutoGenerateColumns="False"/>
</StackPanel>