title: ASP.NET Ajax Toolbox Error Cannot Read property UI of undefined
body: <p>I am trying to learn how to use the Ajax Toolbox with my .net application. I added the toolbox via Manage NuGet Packages and added the following to my web.config file:</p>
  
  <p>add tagPrefix="ajaxToolkit" assembly="AjaxControlToolKit" namespace="AjaxControlToolKit"</p>
  
  <p>whenever I go to a page and try and add an element from the Ajax Toolkit I get an error message "Cannot read property 'UI' of undefined</p>
  
  <p>If I try and add in the ToolkitScriptManager on the page I get an error "Only one instance of ScriptManager can be added to a page"</p>
  
  <p>Any help would be appreciated :)</p>