Too slow when selecting more than 5K rows about xaml-sdk

[bsivanov]

Could you specify which example you are referring to?

[maciz84]

Hi there,

I am referring to the BindingSelectedItemsFromViewModel example From A few years back. The transfer part of the code is too slow. I wouldn't complain if it was an asymc method where I could at least show a loading panel or something

[maciz84]

Has this been updated?

[maciz84]

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

[maciz84]

The code i user is below:

`using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
using Telerik.Windows.Controls;
using System.Collections.Specialized;

public class MySelectedItemsBindingBehavior : ViewModelBase
{
private readonly RadGridView grid = null;
private readonly INotifyCollectionChanged selectedItems = null;
private Boolean isSubscribedToEvents = false;

private static Boolean isAttached = false;


public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.RegisterAttached("SelectedItems", typeof(INotifyCollectionChanged), typeof(MySelectedItemsBindingBehavior), new PropertyMetadata(new PropertyChangedCallback(OnSelectedItemsPropertyChanged)));
public static void SetSelectedItems(DependencyObject dependencyObject, INotifyCollectionChanged selectedItems)
{
	dependencyObject.SetValue(SelectedItemsProperty, selectedItems);
}

public static INotifyCollectionChanged GetSelectedItems(DependencyObject dependencyObject)
{
	return (INotifyCollectionChanged)dependencyObject.GetValue(SelectedItemsProperty);
}

private static void OnSelectedItemsPropertyChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
{
	RadGridView grid = dependencyObject as RadGridView;
	INotifyCollectionChanged selectedItems = e.NewValue as INotifyCollectionChanged;

	if (grid != null && selectedItems != null) {
		MySelectedItemsBindingBehavior behavior = new MySelectedItemsBindingBehavior(grid, selectedItems);
		behavior.Attach();
		isAttached = true;
	}

	//If grid IsNot Nothing AndAlso selectedItems IsNot Nothing AndAlso Not isAttached Then
	//    Dim behavior As New MySelectedItemsBindingBehavior(grid, selectedItems)
	//    behavior.Attach()
	//    isAttached = True
	//End If
}

private void Attach()
{
	if (grid != null && selectedItems != null) {
		Transfer(GetSelectedItems(grid) as IList, grid.SelectedItems);
		SubscribeToEvents();
	}
}

public MySelectedItemsBindingBehavior(RadGridView grid, INotifyCollectionChanged selectedItems)
{
	this.grid = grid;
	this.selectedItems = selectedItems;
}

private void ContextSelectedItems_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
	UnsubscribeFromEvents();

	Transfer(GetSelectedItems(grid) as IList, grid.SelectedItems);


	SubscribeToEvents();
}

private void GridSelectedItems_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
	UnsubscribeFromEvents();

	Transfer(grid.SelectedItems, GetSelectedItems(grid) as IList);

	SubscribeToEvents();
}

private void SubscribeToEvents()
{
	if (!isSubscribedToEvents) {
		grid.SelectedItems.CollectionChanged += GridSelectedItems_CollectionChanged;

		if (GetSelectedItems(grid) != null) {
			GetSelectedItems(grid).CollectionChanged += ContextSelectedItems_CollectionChanged;
		}
		isSubscribedToEvents = true;
	}
}

private void UnsubscribeFromEvents()
{
	if (isSubscribedToEvents) {
		grid.SelectedItems.CollectionChanged -= GridSelectedItems_CollectionChanged;

		if (GetSelectedItems(grid) != null) {
			GetSelectedItems(grid).CollectionChanged -= ContextSelectedItems_CollectionChanged;
		}
		isSubscribedToEvents = false;
	}
}

public static void Transfer(IList source, IList target)
{
	if (source == null || target == null) {
		return;
	}

	target.Clear();

	foreach (object o in source) {
		target.Add(o);
	}

}

}`

[martinivanoff]

Hello,

Thank you for reporting this. We just fixed it and the update will be live within the next week. In the meantime you can use the GridUtilities class from the ChartView BindingSelectedItemsToViewModel example.

Regards,
Martin Ivanov
Technical Support Engineer