RadEditor is an HTML/XHTML editor, but not Visual Studio for web and the requested scenario for displaying and interacting with server controls in its content area are not supported.
Please, note that if you put a server tag in RadEditor the editor will not strip the tag, but will not render it in Design mode. The ASP.NET tags are not HTML tags and the browser is not able to visualize them. The browser cannot visualize XML Tags and when you put <asp:button> in the editor, the server-side framework will not parse the content (as it is part of the editor, not part of the page).
So, instead of sending to the client the HTML tag <input type=button> it will send <asp:button> - which means nothing to the browser.
the Telerik team
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