Top-Level Statements & Global Usings

Modern C# has declared war on "Boilerplate." In the past, writing a simple 5-line program required 20 lines of ceremonial code (namespaces, classes, and main methods). Modern C# allows you to write executable code directly at the root of a file, mimicking the simplicity of Python or Node.js.

1. Life Before Top-Level Statements

Before C# 9, even a "Hello World" needed a complex structure that confused beginners and annoyed professionals.

using System;

namespace MyProject 
{
    class Program 
    {
        static void Main(string[] args) 
        {
            Console.WriteLine("Hello World");
        }
    }
}

2. The Modern C# Way

Now, everything in Program.cs is implicitly wrapped in a hidden Main method by the compiler. You can just start writing!

// Just one line. That's it.
Console.WriteLine("Hello World");

3. Global Usings (Cleaning Up Headers)

Do you get tired of typing using System.Collections.Generic; at the top of every single file? Modern C# allows you to define your imports globally in one place.

// In a file like GlobalUsings.cs
global using System.Text.Json;
global using MyProject.Core.Interfaces;

// These namespaces are now automatically available in EVERY .cs file 
// in your project without needing a single 'using' statement!

4. Interview Mastery

Q: "Can I have multiple files with Top-Level Statements in the same project?"

Architect Answer: "No. You can only have exactly ONE file with top-level statements per compilation unit (project). Because top-level statements are implicitly translated into the static 'Main' method of the assembly by the compiler, having two files with top-level statements would result in a 'Program has more than one entry point defined' compiler error. Usually, we reserve this simplicity for the `Program.cs` file of our entry project."