One of the following two exceptions occur when the BindingOperations.EnableCollectionSynchronization() is used with the ItemsSource of RadTreeListView:
- System.InvalidOperationException: 'Collection was modified; enumeration operation may not execute.'
- System.NullReferenceException: 'Object reference not set to an instance of an object.'
When using the EnableCollectionSynchronization, the corresponding items control should allow updates of the ItemsSource collection on different threads. This is valid if the requirements to use the EnableCollectionSynchronization method are met.
The exception stack traces are:
InvalidOperationException
at System.ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion() in /_/src/libraries/System.Private.CoreLib/src/System/ThrowHelper.cs:line 432
at System.Collections.Generic.List`1.Enumerator.MoveNext() in /_/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/List.cs:line 1130
at System.Linq.Enumerable.SelectEnumerableIterator`2.MoveNext()
at Telerik.Windows.Data.EnumerableExtensions.<SelectRecursive>d__15`1.MoveNext()
at System.Linq.Enumerable.SelectEnumerableIterator`2.MoveNext()
at Telerik.Windows.Data.HierarchicalCollectionViewBase.PopulateInternalList(IQueryable view)
at Telerik.Windows.Data.QueryableCollectionView.get_InternalList()
at Telerik.Windows.Data.HierarchicalCollectionViewBase.get_InternalCount()
at Telerik.Windows.Data.DataItemCollection.get_Item(Int32 index)
at Telerik.Windows.Controls.GridView.Rows.GetRowItemsAtRange(Int32 startIndex, Int32 endIndex)
at Telerik.Windows.Controls.GridView.GridViewVirtualizingPanel.FlatLayoutStrategy.RealizeRows(Int32 startIndex, Int32 endIndex, Double& verticalOffset, HashSet`1& realizedRows)
at Telerik.Windows.Controls.GridView.GridViewVirtualizingPanel.FlatLayoutStrategy.MeasureOverride(Size availableSize)
at Telerik.Windows.Controls.GridView.GridViewVirtualizingPanel.MeasureOverride(Size availableSize)NullReferenceException at Telerik.Windows.Data.QueryableCollectionView.InternalGetItemAt(Int32 index) in Telerik.Windows.Data\QueryableCollectionView.cs:line 3081 at Telerik.Windows.Controls.GridView.Rows.GetRowItemsAtRange(Int32 startIndex, Int32 endIndex) at Telerik.Windows.Controls.GridView.GridViewVirtualizingPanel.FlatLayoutStrategy.RealizeRows(Int32 startIndex, Int32 endIndex, Double& verticalOffset, HashSet`1& realizedRows) at Telerik.Windows.Controls.GridView.GridViewVirtualizingPanel.FlatLayoutStrategy.MeasureOverride(Size availableSize) at Telerik.Windows.Controls.GridView.GridViewVirtualizingPanel.MeasureOverride(Size availableSize)
To work this around dispatch the updates of the ItemsSource collection to the main UI thread.
Dispatcher.BeginInvoke(new Action(() =>
{
// add/remove items from the source collection
}));
The horizontal scrollbar of RadTreeListView is displayed even the setup suggest that it should not be. For example, this happens if you have a single column with its Width set to * which means that the RadGridView should span in the available space without the need of displaying a horizontal scrollbar. To recreate this the RowIndicatorVisibility property should be set to Collapsed. Additional to that there should be a hierarchy and the items should be expanded.
To work this around, you can set a fixed Width for the column. If you want this to be dynamic you can calculate the width on SizeChanged of RadTreeListView
By default the AutoExpandItemsAfterFilter property of RadTreeListView is set to True, which means that when you filter the data, the parents of all found child items will be expanded automatically. However, if you call the CollapseAllHierarchyItems method this functionality stops working.
To work this around, you can reset the ItemsSource property instead of using the CollapseAllHierarchyItems.
A possible workaround would be the following one:
private void RadTreeListView_Filtering(object sender, Telerik.Windows.Controls.GridView.GridViewFilteringEventArgs e)
{
var treeListView = sender as RadTreeListView;
var internalColumns = treeListView.GetType().GetProperty("InternalColumns", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).GetValue(treeListView);
internalColumns.GetType().GetProperty("ColumnWidthsCalculationPending", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).SetValue(internalColumns, true);
}
private void RadTreeListView_Filtered(object sender, Telerik.Windows.Controls.GridView.GridViewFilteredEventArgs e)
{
Dispatcher.BeginInvoke(new Action(() =>
{
var treeListView = sender as RadTreeListView;
var internalColumns = treeListView.GetType().GetProperty("InternalColumns", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).GetValue(treeListView);
internalColumns.GetType().GetProperty("ColumnWidthsCalculationPending", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).SetValue(internalColumns, false);
}), System.Windows.Threading.DispatcherPriority.Loaded);
}
To work this around, you can hide the pointer over background completely. To do this, you can edit the ControlTemplate of RadListView item and remove the Setter from the PointerOver Visual State.
If you press Ctrl+Up/Down to change the selection and currency in TreeListView, the CurrentCellChanged event is fired. However, the e.NewCell property of the event arguments is null.
To get the new cell, use the CurrentCellInfo property of RadTreeListView.
private void RadTreeListView_CurrentCellChanged(object sender, GridViewCurrentCellChangedEventArgs e)
{
var treeListView = (RadTreeListView)sender;
GridViewCellInfo currentCell = treeListView.CurrentCellInfo;
}
Add a mechanism to allow this type of selection. It can be built-in or some events or method overrides can be introduceds in order to be bale to easily interfere and customize the extended selection.
I am using a RadTreeListView with MaterialDesign theme in a Windows WPF application. By default the selected cell is indicated by a grey line at the bottom of the cell. I don't want an indication for the selected cell and used the advise from forum to change the style as follows:
<Style TargetType="telerik:GridViewCell" BasedOn="{StaticResource GridViewCellStyle}">
<Setter Property="CurrentBorderBrush" Value="Transparent"/>
</Style>
This works fine.
But if changing the Windows application with Alt+Tab and then back to my application with Alt+Tab the cell selection (grey underline) is displayed.
An exception is thrown when you try to update the items source of RadTreeListView in an async method.
The following error is observed.
InvalidOperationException: The calling thread cannot access this object because a different thread owns it
To work this around ensure that only the main UI thread updates the item source.
The selected rows of TreeListView are not returned when calling SelectionPattern.GetSelection method.
The problem can be reproduced with RadGridView as well.