This problem is driving me crazy. Im developing a custom module for a customer of us. 

I create a service layer for the controllers. One reference is pointing to system.web.http but this needs Newtonsoft.Json, Version=6.0.0.0 and DNN uses 4.5.0.0

Assembly 'System.Web.Http, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' uses 'Newtonsoft.Json, Version=6.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' which has a higher version than referenced assembly 'Newtonsoft.Json, Version=4.5.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed'    d:\Documenten\documenten_werk\Klanten\AZBIL\DNN\DNN Website\Azbil\packages\Microsoft.AspNet.WebApi.Core.5.2.3\lib\net45\System.Web.Http.dll    AzbilServices

so i searched on the www and found this solution (web.config):

<dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" />
        <codeBase version="4.5.0.0" href="bin\Newtonsoft.Json.dll" />
        <codeBase version="6.0.0.0" href="bin2\Newtonsoft.Json.dll" />
 </dependentAssembly>

i also tried

<dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" />
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="4.5.0.0" />
      </dependentAssembly>

but now DNN is acting strange. The 'add new module' function goes to DesktopModules/internalservices/API/controlbar/GetPortalDesktopModules?category=Common and if i check it, it gives the expected set back. But in Fidler i see /undefined coming back and all my modules lost there names and get the tag undefined.

I found the solution to change the controlbar to the ribbonbar but i can't add a new module for testing. I keeps adding the banner module. And this is a known issue:  https://dnntracker.atlassian.net/browse/DNN-5141

Who can help me. I don't know how to go further.

i changed my web.config to this

   <dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" />
        <!--<codeBase version="4.5.0.0" href="bin\Newtonsoft.Json.dll" />
        <codeBase version="6.0.0.0" href="bin2\Newtonsoft.Json.dll" />-->
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
      </dependentAssembly>

 removed the old dll from the bin folder and added the new one. I still get undefined modules when i try to add a new one.

In fidler i see

http://webtest.orbid.be/azbil/DesktopModules/internalservices/API/controlbar/GetPortalDesktopModules?category=All&loadingStartIndex=0&loadingPageSize=15&searchTerm=

and then i get a 404 http://webtest.orbid.be/azbil/undefined HTTP/1.1