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Binding SelectedItems with Behavior

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GridView

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11 Answers, 1 is accepted

answered on 07 Dec 2010, 03:19 PM

Yeah. Sorry about that. Here is the XAML:

<telerik:RadGridView

ItemsSource=

"{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=telerik:RadPane},Path=viewModel.References.TypeList}"

>

<i:Interaction.Behaviors>

<this:SelectedItemsBehavior

SelectedItems="{Binding RelativeSource={RelativeSource Mode=FindAncestor,

AncestorType=telerik:RadPane}, Path=viewModel.ComplaintTypes}" />

</i:Interaction.Behaviors

</telerik:RadGridView>

The code for the behavior is exactly the same as the blog post. I just renamed it to SelectedItemsBehavior.

I have an ObservableCollection property on my viewModel that is named ComplaintTypes. I have a controller that uses the UnityContainer to resolve an instance of the View...the container injects an instance of the viewModel then I retrieve the viewModel property from the view, and call an initialize method. I have a background worker fetch data from my service and populate it's public properties for binding. Once that is completed (RunWorkerCompleted), then another method is called to add items to the ObservableCollection that is bound to SelectedItems. Stepping through the code, I can see that the ObservableCollection gets the correct items, but they don't appear selected in the grid. The ItemsSource binding in the code above works.

Here is the code that populates the collection once the data has been retrieved via the service from the database.

if (_complaint.Types.Count > 0)

{

foreach (DataLibrary.Type itm in _complaint.Types)

this._types.Add(itm);

RaisePropertyChanged(() => this.ComplaintTypes);

}

I've also tried replacing the foreach loop and assigning it directly:

this._types = new ObservableCollection<DataLibrary.Type>(_complaint.Types.AsQueryable());

answered on 10 Dec 2010, 02:44 PM

OK, I have found a bit more information. Modifying the sample project, I added a button that calls a method on the datacontext to add items to the SelectedItems property. This works as expected, but stepping through, I think what is happening is that the grid automatically selects the first item in the grid by default when it's initialized, so it runs through the GridSelectedItems_CollectionChanged to add that one item, then (I'm not sure about this one), it runs the method again and deselects the first item in the Grid, therefore modifying the bound property.

When I click the new button, it runs the method I created that Adds one item to the SelectedItems property on the Context and it appears as selected in the grid as expected.

So maybe there is something going on with the timing of the control's initialization and binding and when the SelectedItems property on the Context is getting populated with items.

answered on 10 Dec 2010, 06:21 PM

Ok, I hit breakpoints depending on where in my code, I make the changes. I'm using prism, so my code is as follows will hit breakpoints:

_view = _container.Resolve<EditorView>();

region.Add(_view);

_view.viewModel.Initialize(Number);

I can hit the breakpoints and step through the code to add all 4 items to my collection. Then I fall out of my initialize method and I step to the GridSelectedItems_CollectionChanged method on the behavior.

If I reverse the the last two lines of code above so that it calls initialize, then Add, I can't step through the code.

Just another FYI, my initialize Method, uses a background worker to fetch an entity from the dataSource. Once it completes, RunWorkerCompleted is the one that makes the call to AddTypesToCollection which loops through a collection on the entity and adds those items to the bound SelectedItems property.

I just don't know why it keeps resetting the grid once my method completes. In the sample project, If I don't set IsSynchronizedWithCurrent = True, I don't hit breakpoints. I can set it to True, hit the breakpoint and paste that callstack, if you want me to.