Adding Presentation dlls to asp.net (with telerik controls) web app causes problems

Question

I am having some problems with my production asp.net v4.5.2 website when I add new dlls. I am developing on a standalone laptop with Visual Studio 2017 and I just added some telerik document processing library functions that need the PresentationCore and PresentationFramework dlls. On my development machine there was no problem, added the "add assembly" line to my web.config and added the reference in Visual Studio and it worked fine. I added the dlls to the bin folder on the production environment (2008r2 IIS 7.0), uploaded the new code and modified that web.config accordingly now it works but my users are randomly having controls and pictures not load and getting kicked out of the website with a 403 access is forbidden error. The users get kicked out after going through CAC authentication (production is a military server). Sometimes it's right after they login (CAC authenticate) sometimes there a few minutes into doing stuff and then bam, a control doesn't load or the 403 error pops. This happens in both Chrome and IE. The controls or pictures not loading generally are fixed with a refresh (not always though) but the 403 error the users have to reboot their machine to fix. I've even had them clear the browsing data (cache, cookies and ssl state) but they still have to reboot.

When I take those dlls out of the bin folder the problems go away. Google seems to always point to Visual Studio answers and the closest things I found here are adding custom .dll class library to asp.net/C# website and How do references work in ASP.NET WebForms websites (not web applications)? Which didn't help. I think you should also know that I have 2.5 years experience in professional coding and system administration and I am the Lead/Senior (and only) developer and the Sys Admin for this project, please use small words for me. Thanks for any help you can provide.

Answer 1

I figure out what was happening and it wasn't the dlls. Turns out the I was missing a CSS file which caused 404 errors and when enough of those piled up the web app would crash or IIS would give a 403 error. I found this by looking at the event logs for IIS on our production test site. It was so hard to find because that CSS was for 1 particular control and if you didn't navigate to the page with that control enough times it worked fine. I thought it was the dlls because I just added functionality to that control that required them and without that functionality the control was not used as much and so wasn't loaded enough times to cause the error. Not sure why Visual Studio didn't say anything about the missing file but once I removed the call for that CSS file everything worked as expected. I took over this particular code recently and no other place in code are there custom CSS files so I never noticed the call for it. Luckily IIS is set to log everything.