Errors when trying to render window

[Dr. Dualech]

So I've been receiving these errors when trying to get a simple Window to open. The errors are primarily the result of ContextSettings errors and the _window static variable. Some comments and help with the code would be greatly appreciated. Sorry for the size, just open the image in a new tab.

[Laurent]

Your destructor and _window variable are declared but not defined. Google is your friend if you don't know how to define a static member variable.

Intellisense errors are not errors, ignore them.