How to toggle grouping via MVVM binding?

[Brian Sayatovic]

I have a RadGridView whose contents can be usefully viewed grouped or ungrouped, based on a user's whim.  I'd like to expose a Checkbox for the user to toggle the grouping behavior.  Since GroupDescriptors can be added/removed from the RadGridView on-the-fly, this shouldn't be a problem.

However, I'm using MVVM where I expect aspects like this to be bindable from the ViewModel.  Has anyone managed to accomplish what I seek using pure MVVM binding?

[Brian Sayatovic]

I think I just just binding to an ObservableCollection of GroupDescriptors that I either replace, or add/remove from, on the fly:

<RadGridView ... GroupDescriptors="{Binding MyDescriptors}" ... />

[Brian Sayatovic]

Oh no!

System.NotSupportedException: Cannot set read-only property 'Telerik.Windows.Controls.GridView.GridViewDataControl.GroupDescriptors'.

Say it ain't so! 

[Brian Sayatovic]

In lieu of this, I'm making a custom attached dependency property that allows be to binding to a single IGroupDescriptor from my view model and have it added/cleared from the RadGridView's GroupDescriptors, e.g.:

<RadGridView ... local:Grouping.DynamicGroupDescriptor="{Binding MyGroupDescriptor}" ... />

[Pavel Pavlov]

Hello Brian,

Indeed the GroupDescriptors collection is readonly as we do follow some MS standards and typically will not expose a read write collection typed property.

An MVVM friendly way of controlling the grouping would be to use a CollectionViewSource.View as ItemsSource for the RadGridView. RadGridView will respect the grouping state of the CollectionViewSource.

Kind regards,
Pavel Pavlov
the Telerik team

[Brian Sayatovic]

Had I realized that was a possibility, I would've used it first; however, I've already arrived at my solution so I'll stick with it for now.

[Arnaud]

Hello, 

The grouping with ICollectionView as the ItemsSource is fine. But I did not manage to use an alternate display name (the actual column's header or another string property that is not the group Member). With GroupDescriptors I could use the DisplayContent, but as you said the GroupDescriptors can't be bound to the ViewModel...

Any idea ?

 

Arnaud.

[Arnaud]

... and what about the ShowColumnWhenGrouped option ?

Please provide a way to group from ViewModel with respect to the columns definition : Display Header instead of DataMember, Hide column if  ShowColumnWhenGrouped is False, etc... Just as if the column was manually group !

Arnaud.

[Maya]

Hi Arnaud,

You can try working with QueryableCollectionView and create GroupDescriptor instead. So, you can have the following source collection property in your ViewModel:

private QueryableCollectionView clubs;
      public QueryableCollectionView Clubs
      {
          get
          {
              if (this.clubs == null)
              {
                  this.clubs = new QueryableCollectionView(Club.GetClubs());

                  this.clubs.GroupDescriptors.Add(new GroupDescriptor() { Member = "Name", DisplayContent = "CustomName" });
              }

              return this.clubs;
          }
      }

Regards,
Maya
Telerik

[Arnaud]

Hello Maya,

In contrary to ICollectionView the QueryableCollectionView does not support the Filter predicate. The code compiles but the Filter Property raises a runtimeError. Why do you leave it if its not supported ? Could you please help me to filter the QueryableCollectionView ?

Regards, 

Arnaud.

 

[Maya]

Hi Brian,

You can filter the collection quite easily with the help of FilterDescriptors collection. For example:

private QueryableCollectionView clubs;
        public QueryableCollectionView Clubs
        {
            get
            {
                if (this.clubs == null)
                {
                    this.clubs = new QueryableCollectionView(Club.GetClubs());

                    this.clubs.GroupDescriptors.Add(new GroupDescriptor() { Member = "Name", DisplayContent = "CustomName" });
                    this.clubs.FilterDescriptors.Add(new FilterDescriptor() { Member = "Name", Value = "Arsenal", Operator = FilterOperator.IsEqualTo });
                }

                return this.clubs;
            }
        }

In case you want to work with Filter property, you can create your own custom QCV and override it. 


Regards,
Maya
Telerik