I received above mentioned error after changing my project assembly name in Project > Properties > Application > Assembly Name

Any Ideas how to solve it?

I already tried these 2 solutions but none of them worked:

1-Right clicked on my project name in solution explorer and clicked on "Set as Startup Project"

2-Tried to set Startup Project in my project properties page but it is grayed out.

3-Change my Target Framework from 4 to 4.5

CodePudding user response：

I found the problem:

I also mistakenly had changed my Application Type from Class Library to Windows Form Application so changing it back to Class solved my problem.