I am unable to get the List Search Extender from the Ajax Control Toolkit to work correctly. After inserting my WebPart to the page, I get the error: "Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies. The system cannot find the file specified."

I followed the installation instructions for Visual Studio 2010 as found here. I see the AjaxControlToolkit listed in the references section of my solution and I have registered the assembly as shown in my code below.

*EDIT: Additionally, the assembly shows up in the GAC and I added a screenshot of the assemblies in my project package and the corresponding safe control in the Web.config

<%@ Register TagPrefix="asp" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit"%>

<asp:ListBox ID="VendorSelector" runat="server"></asp:ListBox>
<asp:ListSearchExtender id="LSE" runat="server"
  PromptText="Type to search"




  • 2
    Is the assembly in the GAC? If so, you need to use the full 4 part assembly name (the one with the PublicKeyToken and stuff).
    – James Love
    Aug 5, 2012 at 21:28

2 Answers 2


I added the version and public key of the assembly in my Register statement. No more runtime errors.

  • 1
    I should also note that beware when adding assemblies to the project using that interface - if any other solutions rely on that assembly and you retract your solution, it will pull out that assembly from the GAC and break the other solutions.
    – James Love
    Aug 6, 2012 at 15:38
  • also when adding any dll to the gac allway do an iis reset!
    – Ali Jafer
    Oct 15, 2012 at 8:03

It appears that the version of the AJAX toolkit you are using is incorrect. I had this issue and after downloading and installing the correct version for my target sharepoint installation, and it worked. Hope this helps.

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