The “RenderingMode” or "rendermode" property of the RadComboBox not present. so is this removed and some other alternative property is present for this.
I want to set the rendering mode to native but was unable to do it.
As from Q1 2013 RadComboBox introduces the RenderMode property and from Q3 2011 RadComboBox introduces the RenderingMode property.So please upgrade your telerik version to get these two properties.
The information about the new features, changes and backward compatibility
issues if any for all the RadControls is available on Telerik's site, section
Products > ASP.NET AJAX Controls > What's New > Release History. You can choose an appropriate RadControls version from the Release History where all the RadControls are listed along with the new features, changes and bug fixes that are added to the corresponding control.