Cannot load any .xnb files after upgrading to monogame 3.5

I just upgraded to 3.5 and attempted to build my game.
The game built and ran perfectly before upgrading.

When I attempt to import a texture with Content.Load, I get the following ContentLoadException:

Could not load BackgroundTexture asset as a non-content file!

With the following Inner ContentLoadException:

Asset does not appear to be a valid XNB file. Did you process your content for Windows?

Here is the code:

menuResources = new MainMenu.Resources( Content.Load<Texture2D>("BackgroundTexture"), Content.Load<Texture2D>("RunecraftLogo"), Content.Load<Texture2D>("RoundButtonTexture"), Content.Load<SpriteFont>("MenuFont"));

Regardless of what file I attempt to load, this exception occurs.

I have ensured that the platform is set to Windows and rebuilt my content with the content pipeline. I have performed a clean build of the game to ensure that the newly built content files are copied. Nothing has solved it.

Any idea what is going on?

Are there any build errors when compiling the content? Also, have you made sure that you are referencing the updated Monogame libraries from the same installation folder as the content pipeline (ie. did you install 3.5 elsewhere)?

I had the same issue, my topic:

First, try this steps: Upgrading to MonoGame 3.5

If it doesn’t work, try to do what I did. I created a new MonoGame 3.5 Project and I moved the entire project files to there. I choose the MonoGame Cross Platform Desktop Project, but you can use the MonoGame Windows Project, you just need ensure that the bug doesn’t happen on the new project before moving everything.

There were improvements made to the .targets files in relation to building and copying content files to the output directory. I would suggest creating a new project with the latest templates and comparing the csproj files. I can’t recall right now what the changes were, but that should give you a good idea of what needs to be done.