You may encounter the following error especially when you have just upgrade your Sitecore Instance or copying DLLs to the Bin folder.
“The type initializer for ‘Sitecore.Install.Serialization.IOUtils’ threw an exception.”
This blog post is very short because in order to solve the above error only 2 steps are required. First one is verification and second is copy and paste the missing dll.
In order to solve this issue, you need to check if you have the following DLL in your bin folder:
If the DLL is not present, you need to copy it from a working environment and paste it in the Bin folder of the instance which is returning the above error.
If the issue still persist, you may need to compare the configuration files and DLLs of a working Sitecore instance and the corrupted one.
I personally use WinMerge and until now, it has helped me in identifying issues between configuration files.