Reading Command-Line Arguments

In this lesson you will learn how to read command-line arguments in C#, so values can be passed in from outside when the program runs. This is for anyone searching for "C# command-line arguments how to use".

Declaring Main(string[] args) gives you the command-line arguments through the parameter of Main. It is essential whenever you want a command-line tool whose options can be switched at run time.

The sample code checks whether any arguments were supplied with args.Length > 0, and uses a ternary operator to take args[0] as the name when there is one and fall back to "Anonymous" when there is not.

A common stumbling block for beginners is forgetting the case where no argument was supplied. Reaching straight for args[0] errors out when nothing was passed, so check args.Length first.

In real-world development, this also serves as the foundation of automation scripts that branch on the values supplied at run time.

📖 Reference code

using System;

class Program {
    static void Main(string[] args) {
        string name = args.Length > 0 ? args[0] : "Anonymous";
        string age = args.Length > 1 ? args[1] : "Unknown";
        Console.WriteLine("Name: " + name);
        Console.WriteLine("Age: " + age);
    }
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run C# directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).