Can't delete tab/buttons from form

Question

I have a C# project which runs absolutely fine. I want to delete a tab and all buttons inside it. I tried deleting it by selecting the tab and saving, it gets deleted..but whenever I try running the build..the tabs and all buttons reappears. I even tried deleting code for each button..but that didn't helped either :(

The project also references to some external dll. I tried removing those references..but still that tab and button appears.. :(

Please can someone tell me why it's happening?

I want to delete "APP" tab and all buttons inside it.


Thanks in advance.