ComboBox with Virtualizing Panel and IsFilteringEnabled not Working

[Nivid]

Using virtualizing panel as itemspanel does not resize the dropdown height and also another behavior i got was it does not filter the items as it focused the correct item but in the case when it has lots of items in my  case 5000 items it searches correctly but does not filter. Can someone suggest how to fix this issue. I have created a sample project with this. The project has two dropdowns with seperate behaviors 

1) Dropdown height is not resizing on filtering.
2) Large Collection finds the item but does not filter the items.

Sample Project can be found here
https://www.dropbox.com/s/q2my5hj9lyrqrmp/RadComboBoxDemo.zip

I have IsFilteringEnabled set to true

<Style TargetType="{x:Type controls:ComboBox}">
            <Setter Property="IsEditable" Value="True" />
            <Setter Property="VerticalAlignment" Value="Center" />
            <Setter Property="Margin" Value="5" />
            <Setter Property="Grid.Column" Value="1" />
            <Setter Property="IsTextSearchEnabled" Value="True" />
            <Setter Property="TextSearchMode" Value="Contains" />
            <Setter Property="IsFilteringEnabled" Value="True" />
            <Setter Property="StaysOpenOnEdit" Value="True" />
            <Setter Property="ItemsPanel">
                <Setter.Value>
                    <ItemsPanelTemplate>
                        <VirtualizingStackPanel/>
                    </ItemsPanelTemplate>
                </Setter.Value>
            </Setter>
        </Style>

[Vladi]

Hello Nivid,

I noticed that you posted a support ticket about the same issue, is it possible to continue the discussion there? I will post the response from the other ticket here too.

We tested the issues but we weren't able to reproduce the first issue.

About the second issue, virtualization with filtering is not supported in the current version of the control. It is worth mentioning that recently we released a new RadAutoCompleteBox control that has a build in filtering feature with virtualization and could be useful in your scenario. You can check our RadAutoCompleteBox online demos here.

Greetings,
Vladi
the Telerik team