Today, I want to build this example, https://github.com/dalefugier/SampleCsWpfPanel.
However, the result is that RhinoWindows don’t be found.
I looked for it in …\Rhinoceros 5.0 (64-bit)\System.
Anyone know where I can find it.
It should be there (it is on my system) - have you installed the latest service release (SR11)?
My version is indeed SR11. 
It is my folder below.
Sorry, I know the reason. 
So, the 32-bit can’t use WPF???
The RhinoWindows.dll assembly is an AnyCPU assembly according to the CorFlags.exe utility, so it should also be usable by 32-bit Rhino. I think @stevebaer is the right person to ask why the RhinoWindows.dll assembly is not in the 32-bit Rhino distribution.
I have it installed here (both 32-bit and 64-bit Rhino 5 SR11). You might consider re-installing…