I haven't worked on my extension since before the move to Umod. Today i open up the project and changed a few things and tried to load the extension on my local server and i'm getting the error "Failed to load extension Oxide.Ext.VmeCore (Specified assembly does not implement an Extension class)".

This is odd since the assembly does have a class in the 'Oxide.Ext.VmeCore' namespace that implements the extension class and the assembly was being loaded before i updated the server and oxide. The class is public. I'm using all the latest nugest and compiling for .Net 4.6. 

Could you show an example of the extension where you are defining the namespace and such for the main Extension .cs file? Also, which game are you building for?

Hi Wulf, 
The extension is file "VmeExtension.cs". Image below shows how the extension is defined. 
The extension is for Rust.

And how about the VmeCore file? That's the one that the error is mentioning. The VmeCore should be inheriting CSPlugin.

So, the assembly is being compiled to file name "Oxide.Ext.VmeCore" which is what oxide is complaining about. There doesn't exist a .cs file or class called "VmeCore" in the assembly and "VmeCore" is the root namespace relative to "Oxide.Ext.".
I'm not sure i understand why it should be inheriting CSPlugin plugin as it's an extension

Each extension has an internal plugin still, which is what it inherits CSPlugin for.

I understand what you mean, there are plugins in the extensions and they are all inheriting from the CSPlugin class. The problem isn't with the plugins, but rather with the extension itself. As i mention, the extension was working just fine until i updated the server and the oxide nugets.

I tried creating a class called "VmeCore" which inherits from CSPlugi, but this did not solve anything. Would you be able to provide a code snippet of what you mean?

Plugin and extension loading hasn't changed in years, so I'm not sure why you'd be having an issue now. You can see examples of our extensions at https://github.com/theumod/umod.rust/tree/oxide and the other repositories at https://github.com/theumod/umod.rust

Which packages are you referencing?

Okay, so after some head scratching it seems that the error was the cause of all my problems, it was very misleading causing me to search in the wrong place. 
My extension had a dependency which i forgot to move to the \Managed folder and when the oxide core tried to load it, my extension could not find the dependency and therefore panicked, it them seems that oxide handles this as not having implemented the extension class.
If i have some time soon i'll do a pull request to help make the error point in the right direction.
This would explain why empty extensions were working and once i added my custom extension class and dependency i would get the error ( I was going mad!)

Merged post

Is there a repo for Oxide that displays full debug messages and exceptions details? All the repo's are in Umod namespace and i can therefore not use it with the current versions of oxide

The "oxide" branches contain the pre-refactored code, but we won't be accepting anything to those as we are moving to uMod.