I'll help you create a C# window with rounded corners. Let me first check what kind of project structure you have.

I'll create a C# Windows Forms application with a rounded window for you.

Created a C# Windows Forms application with a rounded window. The window has:

• No title bar (FormBorderStyle.None)
• 20px corner radius for rounded corners
• 400x300 size
• Light gray background
• Optional border drawn in paint event

Run with dotnet run to launch the application.