There are several projects in the solution. Only in one project I have a Program class with the Main method. Always everything was fine, and now gives out such a mistake. I can not understand what the problem is. It seems to be all right.
Answer 1, Authority 100%
It can be seen that an error in the project Entity.
The entry point is always required for the “Console Application” and “Windows Applications”. If you entity thinks like one of these two options, add the corresponding static method into it, without it. Because any application should begin with any entry point.
But if you think this project as a “classes library”, then go to the project properties and select “Output” – “Class Library”. In this case, the entry point is not required.