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Binding RadGridView's SelectedItem(s) and SelectedCells (MVVM) using a RadContextMenu

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This is a migrated thread and some comments may be shown as answers.

Abhinav asked on 01 Nov 2016, 02:03 PM

Hi,

We are currently using Telerik's RadGridView control with extended/mixed mode selection enabled.

Is there any way to Bind directly to the:

a) SelectedItem/SelectedItems

b) The SelectedCells' Column and Item(s) properties

c) FilterDescriptors (to suspend/resume notifications)

Using a RadContextMenu for Pure MVVM?

We are currently using an approach with references RadGridView UI elements via the ViewModel, which we'd like to avoid. We have also considered the SelectedItems approach through a behavior, as illustrated here:

http://www.telerik.com/blogs/how-to-synchronize-your-ui-selected-items-with-your-data-context-using-mvvm-and-blend-behaviors-for-silverlight-and-wpf

However, the performance of the selection slows the larger the number of items highlighted, since the behavior is triggering the Transfer method in the behavior for each row highlighted in the RadGridView. We'd like to avoid using a behavior, if possible, as our users are working with large datasets and will need to be able to selected 1M+ rows at a time.

Currently, we are using this approach, where we are able to pass the RadGridView to the ViewModel as a CommandParameter from a RadContextMenu in its entirety:

<telerik:RadGridView Grid.Row="1"
Name="dtgMyData"
ItemsSource="{Binding Path=MyDataCollection}"
AutoGenerateColumns="False"
IsReadOnly="False"
RowIndicatorVisibility="Visible"
HorizontalAlignment="Stretch"
SelectionMode="Extended"
SelectionUnit="Mixed">

...

<telerik:RadContextMenu.ContextMenu>
<telerik:RadContextMenu x:Name="MyDataGridContextMenu">
<telerik:RadContextMenu.Items>
<telerik:RadMenuItem Header="Filter Selected" Command="{Binding DataContext.FilterSelectionCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type telerik:RadContextMenu}}}" CommandParameter="{Binding Path=UIElement, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=telerik:RadContextMenu}}"/>
</telerik:RadContextMenu>
</telerik:RadContextMenu.ContextMenu>

...

...<columns>...

Where the Command and CommandParameters are bound to the ViewModel.

Is there a way to avoid binding to the ViewModel directly referencing UI controls using a RadContextMenu without using behaviors? For example, is there another Binding option for the CommandParameter above that is shown to reference the entire RadGridView, such that we can reference SelectedCells.Item(s) or SelectedItem/SelectedItems bound to our Model (i.e. MyData) directly, and if at all possible, the Column and/or Column FilterDescriptors without having to use code-behind and avoiding the use of a behavior?

Kind regards

13 Answers, 1 is accepted

answered on 04 Nov 2016, 01:18 PM

Hello Abhinav,

Thank you for the detailed description of your requirement.

The SelectedItems, SelectedCells and FilterDescriptors collections exposed by RadGridView are not dependency properties, thus binding directly to them is not possible. I am afraid, that we are not planning to modify this default design of the control. With this in mind, implementing an attached behavior as demonstrated in the blog post to which you referred would be the appropriate approach for this requirement. You can also take a look at the Binding SelectedItems from ViewModel SDK example for further reference. It can be reviewed through the SDK Browser.

Hopefully, this clarifies your concerns.

Regards,
Stefan X1
Telerik by Progress

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answered on 08 Nov 2016, 02:41 PM

Hi Stefan X1,

Thanks again for your quick reply.

We currently using reflection to get the SelectedCells so that we can apply custom filters programmatically through a ContextMenu click event on the RadGridView which filters the grid based on the cells the user had selected, however, we were hoping to change this code-behind 'click event' to a ViewModel 'command', without directly referencing the UI elements in the ViewModel. We are able to bind SelectedItems, which exposes the underlying model, to a command in the ViewModel using an EventTrigger and we were hoping to do this with SelectedCells, as well. It seems SelectedCells is wrapped by an internal type, so we are not able to expose the properties without using reflection. We were hoping to return a user object from a custom IValueConverter, returning the Columns and the Items of the SelectedCells, as does the SelectedItems.

Kind regards

answered on 11 Nov 2016, 11:40 AM

Hello Abhinav,

Thanks for this clarification.

The SelectedCells collection of RadGridView is of type GridViewCellInfo, which exposes the Column and Item properties. Generally, they should be enough for implementing the filtering you need. Can you please share some details on which are the properties you need and you are trying to access through reflection?

As to reacting to a UI event in the view model, you can benefit from the EventToCommandBehavior that we provide. Can you please check it out and let me know whether it corresponds to your needs?

Regards,
Stefan X1
Telerik by Progress

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answered on 14 Nov 2016, 02:39 PM

Hi Stefan X1,

Thanks again for your input.

The EventToCommandBehavior still requires passing a UI element to the ViewModel.

We're attempting to use an IValueConverter using a custom object to convert from the GridViewCellInfo object. Using this converter, we are internally transposing the GridViewCellInfo object into a custom container object that we created to use as the Model, i.e. a

[ValueConversion(typeof(IList<GridViewCellInfo>), typeof(SelectedCellsContainer))]

The converter would have worked except for the fact that the Command is triggering first, then the converter. Here is an example of our usage in XAML:

<RadGridView>

...

<i:EventTrigger EventName="SelectedCellsChanged">
<i:InvokeCommandAction Command="{Binding SelectionCellsChangedCommand }" CommandParameter="{Binding ElementName=dtgMyDataGrid, Path=SelectedCells }" />
CommandParameter="{Binding ElementName=dtgFills,Converter={StaticResource SelectedCellConverter},Path=SelectedCells }"
</i:EventTrigger>
...

</RadGridView>

Could you please shed some light as to why the Command is triggering before the Converter? Do we need to bind the CommandParameter to an ancestor for the InvokeCommandAction, as in:

CommandParameter="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGridCell}},Converter={StaticResource DataGridCellToRowActionParametersConverter}}">

I hope this explains things clearly.

Kind regards.

answered on 23 Nov 2016, 05:19 PM

Hi Stefan X1,

We've managed to develop an approach to capture the Grid's CellInfoCollection from a Command in our ContextMenuItem, by way of:

<telerik:RadMenuItem Header="Filter Selected" Command="{Binding DataContext.FilterSelectionCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type telerik:RadContextMenu}}}" CommandParameter="{Binding Path=UIElement.SelectedCells, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=telerik:RadContextMenu}}"/>

Here, we are passing SelectedCells to the VM and converting the cells to a custom model in the VM. We will go with this approach for now.

We've benchmarked the attached behavior approach and have found it to not be responsive enough for our user's needs.

Thanks very much for your help.

Kind regards.