Today I found a mistake that made me lose almost an hour until I realized that was happening.

I am developing a project in WPF. In this project I have a main window and then I’ve created me a folder with multiple user controls. The problem has come when I’ve put in the window design mode and and tried to drag her user controls that had created.

To drag them up didn’t let me drop them, it is as if the window was blocked. However the own controls WPF if that allowed me to place them. If I added them manually in the XAML then the designer gave me an error, in particular this:

Unable to load the metadata for assembly 'MY_ASSEMBLY'. This assembly may been downloaded from the web.

But the strange thing is that if you ran the application it worked perfectly.

After testing thousands of things I’ve noticed the problem that was the project on which he was working on a network drive, and not on a local disk.

It had opened the project from the network drive and everything works correctly, in fact at home I usually work like this because I have all the projects on a server and access across different computers via shared drives. I never had problems until today. I have copied the project to a local disk and everything has been solved.