Create a C# Windows Desktop App in 9 Lines — No Visual Studio Needed

If you’re new to C# and especially desktop development, here’s how easy it is to get started on a modern Windows 10/11 PC. This way of creating a Hello World C# program doesn’t involve installation of any heavy IDE like Visual Studio or the .NET 8/9 SDK.

In fact, most recent Windows versions already come with .NET Framework 4.x preinstalled, including the classic C# compiler at a location like this:

C:\Windows\Microsoft.NET\Framework\v4.0.30319

The exact folder may differ depending on your system but it usually contains csc.exe, the built-in compiler that can compile simple console or desktop apps. You can add this folder to your PATH environment variable (temporarily or permanently) so that csc is available from the command line:

set PATH=C:\Windows\Microsoft.NET\Framework\v4.0.30319;%PATH%

We will be using this classic, old-school style of programming (similar to writing C programs with gcc or turboc) — a great way to get acquainted with a new language.

Step 1: Create the source file

Make a new folder anywhere on your drive. Inside it, create a file named Program.cs using Notepad, VS Code, or any editor you like:

using System;
using System.Windows.Forms;

class Program {
	public static void Main() {
		Form frm = new Form();
		frm.Text = "Hello";
		frm.ShowDialog();
	}	
}

In just nine lines of C# code, without using any IDE, you now have a working “Hello World” desktop app with no additional dependencies.

Step 2: Compile and run

Open Command Prompt in your project folder and run:

csc Program.cs
Program

The first line tells the C# compiler (csc.exe) to build the app into Program.exe. The second one runs it. You can also double-click Program.exe in File Explorer.

By default, a console window appears behind the form. To build a GUI-only app without the console, recompile with the /target:winexe parameter:

csc /target:winexe Program.cs

What’s next?

In upcoming posts, we’ll add more features such as menus, buttons, event handlers, and even database access with ADO.NET. But for now, enjoy this milestone: you’ve built your very first Windows desktop app in C#!