Thank you for update.

Hello,

this does not happen with the product/project as it is, "out of the box". It looks like that you have referenced, directly or indirectly, the JetBrains.Annotations package.
I suggest to remove that reference.

If you cannot do it for some reason, your other options are:

• Comment out or remove the [NotNull] and [CanBeNull] attributes. They do not affect the program behavior, they are just for analysis.
  
• Use extern aliases to tell the compiler which one of the types you want to use (it doesn't really matter which one, but the compiler needs to have a way to decide). See e.g. stackoverflow.com/questions/3018419/class-with-same-name-in-two-assemblies-intentionally .

Also note that the error message you provided have several typos in it and is not complete. You should copy/paste such information, as the precise and full text is crucial for our analysis.

In addition, that (probably unrelated to this issue), the minimum supported .NET Framework version is 4.6.2. This is also how the project ships. Change the target framework to .NET Framework 4.6.2.

Best regards