Menu scroll arrow close the Panel when I release the mouse button

[ezequiel]

I've a RadSplitter with a left panel and right panel, and in the right panel i've a RadMenu. 

The problem si that, in the scroll of RadMenu item, i can click and hold the down arrow to scroll faster and  when i scroll all the way to the bottom of the list, the left panel disappears when i let go of the mouse button.

I don't understand what relationship there can be between one thing and another.
Any suggestions to solve the problem?

 

 

[ezequiel]

I would like to add that this happens when the _onLinkMouseUp event is executed on any menu item, without first clicking.

[ezequiel]

Now I also found that in each click on the menu, the left panel disappears and reappears during the postback.
This began after migrating from Telerik 2014 to 2020.

[Peter Milchev]

Hello,

There was a bug in the Visual Studio Extensions for version R1 2020 where the Upgrade wizard would set the Lightweight render mode as the default, instead of Classic. You can verify that by using the script from Determine mixed RenderModes:

• https://docs.telerik.com/devtools/aspnet-ajax/knowledge-base/common-determine-mixed-render-mode

If this is the case, please remove the following line from all the appSettings sections in the web.config files you have where you did not intentionally set this:

 <add key="Telerik.Web.UI.RenderMode" value="lightweight"/>

If the issue persists, try to downgrade to the old version and check if the behavior changes.

If there are any other changes you have made in your code apart from upgrading the Telerik version, please prepare a simple example with a simple Splitter and Menu and attach them in an official support ticket. That would allow us to run and investigate your exact scenario and provide more accurate and specific suggestions to resolve this issue. 

Regards,
Peter Milchev
Progress Telerik