Visual Studio creates and modifies .Designer.cs files automatically for WinForms forms. Those files have a comment telling developers not to edit them by themselves. Also, it seems that, most people think that, developers should not edit those files by themselves (Manual editing of *.designer.cs file). When using Visual Studio, this is fine. However, now I am using Mono and MonoDevelop, to try to port some WinForms programs to Linux. Unfortunately, MonoDevelop does not have a WinForms designer. So, when using MonoDevelop on Linux, I have to edit those files by myself.