Thank you for clarifying the issue. The problem you observe is due to setting the DockedPaneId to Nothing only. In this way the sliding pane will be undocked but nothing will make it resize to the correct size as the panes preserve their width and height after a postback. To achieve the desired scenario you can dock/undock the slidingpane registering script which docks/undocks the pane client-side in the way it is demonstrated in the Client-Side API online example
or set the height property of the splitter's panes after undocking the pane server-side with DockedPaneId set to Nothing. For your convenience I have attached a sample page which demonstrates both of the above suggestions.
The RadSplitter.Net2.dll is the dll for RadSplitter for ASP.NET (the classic version). If you want to use the ASP.NET AJAX version of the splitter you should download the RadControls for ASP.NET AJAX suite. It provides the Telerik.Web.UI.dll which contains all Telerik's ASP.NET AJAX controls. To use RadSplitter for ASP.NET AJAX you need to add the Telerik.Web.UI.dll in the bin folder of your WebSite.
The RadControls for ASP.NET AJAX are created on the top of ASP.NET AJAX and for this reason a ScriptManager control is required on the page to registers the needed scripts as well as the Web.config file should contain the configuration settings for an Ajax-enabled website.
If you create an Ajax-Enabled WebSite
the Web.config file will contain the needed configuration settings for an ASP.NET AJAX website and you will not need to add them manually. Otherwise, if you choose the ASP.NET web site
option you will need to modify the Web.config file manually. You can take a look at the following link
which describes how the Web.config file should be configured when using ASP.NET AJAX.
I suggest you use this help article
If you have other questions, do contact us again.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.