I was working on some project in Visual Studio 2003 with many user controls in it and suddenly, I found that I cannot open any control with Forms Editor. When I double-click on the file, it opens with CSharp code editor only. I'm still unsure how did this happen, but after looking at ".csproj" file in notepad, I have found how to fix this. Each file in .NET project is described in separate "File" node inside project file (or "Compile" node in Visual Studio 2005/2008), like in the screenshot below: Note, the SubType attribute -...