Telerik RadControls for ASP.NET AJAX is the successor of RadControls for ASP.NET. Just as ASP.NET AJAX is the future of ASP.NET, RadControls for ASP.NET AJAX is the future of RadControls for ASP.NET. Furthermore, the new suite of controls paves the way for seamless integration with the new Microsoft framework. The RadControls for ASP.NET AJAX suite is built on the top of ASP.NET AJAX and follow the ASP.NET AJAX conventions.
There should not be a problem using classic and asp.net ajax versions of the controls in one website. Nevertheless, we recommend using controls from one suite as they are designed and aimed to work together. What is more, we recommend using the ASP.NET AJAX versions of the controls as all future development and improvement will be concentrated on them and most of the bugs related to the ASP.NET versions are fixed in the ASP.NET AJAX ones
Let us know in case you experience any other problems. We will be glad to help you.
All the best,
the Telerik team
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