Getting TypeLoadException when trying to replace door code

[VapidLinus]

I'm trying to replace the main door in the game, so I simply override the door by putting this in my /defs folder folder:
https://gist.github.com/VapidLinus/ff8ba5a9a8984b3c5bdf

As you can see on line 5, I'm replacing the door class with my own custom class:
<thingClass>VBuilding_Door</thingClass>

So, I've called my custom door class VBuilding_Door. It's identical to the one that comes in the /Source folder, except for formatting and that I'm forcing isOpen to true on the Tick() method.
Here's the source for VBuilding_Door in case you need it:
https://gist.github.com/VapidLinus/1f3fbc288cff6860d83d

However, when loading my mode, I get this error:


I'm guessing it has something to do with the overriden (as in the source of the door) GetCommands<T> method. But I don't understand what or why. It simply says it couldn't load  the type, as you can see in the error.

Any help or thoughts would be appreciated!

[JuliaEllie]

when you use your own classes you have to use <thingClass>namespace.classname</thingClass>

[VapidLinus]

when you use your own classes you have to use <thingClass>namespace.classname</thingClass>

My mod files were in the default RimWorld namespace, so I moved my code to my own new namespace and did what you said. Still didn't work, however. But I found the solution on my own, I had to change the compile version of .NET to 3.5 instead of 4.0. This was a bit of a hassle to do on Windows 8, but I eventually got it to work.