Update TreeViewMenuItem when ItemsSource changes for HierarchicalDataTemplate

[OlavXO]

We have a problem updating the text for a TreeViewItem when the underlying datasource changes.

Here is our xaml (a bit simplified, removed unrelevant code like the "SystemTemplate"):

<UserControl.Resources>

    <telerikControls:HierarchicalDataTemplate x:Key="ChildTemplate" ItemsSource="{Binding System}" ItemTemplate="{StaticResource SystemTemplate}">
            <TextBlock Text="{Binding Name}" />
        </telerikControls:HierarchicalDataTemplate>

        <telerikControls:HierarchicalDataTemplate x:Key="ParentTemplate" ItemsSource="{Binding Child}" ItemTemplate="{StaticResource ChildTemplate}">
            <TextBlock Text="{Binding Name}" />
        </telerikControls:HierarchicalDataTemplate>
</UserControl.Resources>


<Grid x:Name="LayoutRoot" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
    <telerikNavigation:RadTreeView x:Name="rtvTreeMenu" ItemsSource="{Binding Parents}"
                                       IsLoadOnDemandEnabled="True"
                                       ItemTemplate="{StaticResource ParentTemplate}"
                                       LoadOnDemand="TreeMenu_LoadOnDemand"
                                       ItemPrepared="TreeMenu_ItemPrepared"
                                       SelectionChanged="TreeMenu_SelectionChanged"
                                       SelectedValuePath="{Binding Id}">
    </telerikNavigation:RadTreeView>
...

 

‘Parents’ is a property of the type ObservableCollection<Parent> in the class the DataContext is bound to, and Child is an ObervableCollection<Child> property in the Parent class.

The user can change the Name property of a Child object (not directly in the TreeView, but another place in the application), thus we need to update the TreeView to show these changes.

We’ve tried to just fire the propertyChanged like this, but nothing happens (although it works when we add a new Child):

propertyChanged(this, new PropertyChangedEventArgs(“Parents”));

Thanks,

Olav

[Valentin.Stoychev]

Hi Olav Dahl,

Your Parent and Child classes need to implement INotifyPropertyChanged interface in order the changes in them to reflect into the RadTreeView.

Here is a classic example of INotifyPropertyChanged implemention:

public abstract class TaxonomyViewModel : INotifyPropertyChanged
    {
        public Taxonomy Taxonomy { get; private set; }

        private bool isExpanded;
        public bool IsExpanded
        {
            get { return isExpanded; }
            set
            {
                isExpanded = value;
                OnPropertyChanged("IsExpanded");
            }
        }

        private bool isSelected;
        public bool IsSelected
        {
            get { return isSelected; }
            set
            {
                isSelected = value;
                OnPropertyChanged("IsSelected");
            }
        }
        …
    }

Please let us know if you have more questions on that.

Regards,
Valentin.Stoychev
the Telerik team

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[OlavXO]

Thanks for leading me in the right direction,

We actually did implement the INotifyPropertyChanged interface for our objects. The problem was that our implementation of it (and my understanding of it) was wrong ;) Anyway we still have a problem when the bound property has a path like SystemType.Name like the one described under:

<telerikControls:HierarchicalDataTemplate x:Key="SystemTemplate" ItemsSource="{Binding Component}" ItemTemplate="{StaticResource ComponentTemplate}">
            <TextBlock Text="{Binding SystemType.Name}" />
</telerikControls:HierarchicalDataTemplate>

<telerikControls:HierarchicalDataTemplate x:Key="ChildTemplate" ItemsSource="{Binding System}" ItemTemplate="{StaticResource SystemTemplate}">
            <TextBlock Text="{Binding Name}" />
</telerikControls:HierarchicalDataTemplate>

 

But I guess this probably isn't a problem specifically to radTreeView or HierarchicalDataTemplate...

Thanks,

Olav

[Valentin.Stoychev]

Hi Olav Dahl,

I'm not sure I fully understand your question. Can you elaborate a little bit more on it?

Thanks!

Best wishes,
Valentin.Stoychev
the Telerik team

Instantly find answers to your questions on the new Telerik Support Portal.
Check out the tips for optimizing your support resource searches.

[OlavXO]

Sorry, there was not really a question in there. Anyway I found the problem and it had nothing to do with the radTreeView. It was just that the SystemType property of the System did not fire propertyChanged (or it did before, but the service reference got updated and erased the manually edited auto-generated file ;), and therefore the radTreeViewItem text was naturally not updated.

 

Olav

[qian]

Valentin.Stoychev


we can use 

class cls_3
{
     public  <t> rec
     public   IEnumerable < cls_3>  recs
    {
      get ..
    }

}

binding HierarchicalTmplate     ,

How can let the cls_3  :  INotifyPropertyChanged
 and set NotifyPropertyChanged  ?


qian weng

[Petar Mladenov]

Hello qian,

When binding a collection to a RadTreeView, it`s a good practice that it inherits from ObservaleCollection.
I am attaching a code snippet demonstrating a usual ViewModel class. Please let us know if this is what you need.

public class DataItem
    {
        public DataItem()
        {
            Children = new ObservableCollection<DataItem>();
        }
        public ObservableCollection<DataItem> Children
        {
            get;
            set;
        }

        private string header;
        public string Header
        {
            get { return header; }
            set
            {
                header = value;
                RaisePropertyChanged("Header");
            }
        }


        public event PropertyChangedEventHandler PropertyChanged;
        protected void RaisePropertyChanged(string propertyName)
        {
            var handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }

All the best,
Petar Mladenov
the Telerik team