Main method as entry point in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this C# program?

Consider this C# program with a Main method. What will it print when run?

C Sharp (C#)

using System;
class Program {
    static void Main(string[] args) {
        Console.WriteLine("Hello from Main!");
    }
}

A Hello from Main!

B No output, program compiles but does nothing

C Compilation error: Main method missing return type

D Runtime error: Main method not found

💡 Hint

The Main method is the entry point and runs automatically.

The Main method is the starting point of a C# console application. It runs and prints the string to the console.

❓ Predict Output

intermediate

What happens if Main method has wrong signature?

What will happen if the Main method is declared without static keyword in C#?

C Sharp (C#)

using System;
class Program {
    void Main(string[] args) {
        Console.WriteLine("Hello");
    }
}

A Program compiles but does nothing

B Program runs and prints Hello

C Runtime error: Main method not found

D Compilation error: Main method must be static

💡 Hint

Main method must be static because it is called by runtime without an instance.

In C#, the Main method must be static because the runtime calls it without creating an object instance. Omitting static causes a compile-time error.

❓ Predict Output

advanced

What is the output of this overloaded Main method program?

This program has two Main methods. What will it print when run?

C Sharp (C#)

using System;
class Program {
    static void Main() {
        Console.WriteLine("Main without args");
    }
    static void Main(string[] args) {
        Console.WriteLine("Main with args");
    }
}

A Main with args

B Main without args

C Compilation error: duplicate Main methods

D Runtime error: ambiguous entry point

💡 Hint

When running from command line, Main with string[] args is called by default.

The C# runtime calls the Main method with string[] args if it exists. So it prints "Main with args".

🧠 Conceptual

advanced

Which Main method signature is valid as entry point?

Select the only valid Main method signature that can be used as the entry point in a C# console application.

A static int Main()

B public static void Main(string[] args)

C void Main()

D public void Main(string args)

💡 Hint

Main must be static and can have string[] args parameter.

Valid Main signatures include static void Main(string[] args) or static int Main(). The method must be static and have correct parameter types.

❓ Predict Output

expert

What is the output of this program with async Main?

This program uses async Main method. What will it print when run?

C Sharp (C#)

using System;
using System.Threading.Tasks;
class Program {
    static async Task Main() {
        await Task.Delay(100);
        Console.WriteLine("Async Main finished");
    }
}

A Runtime error: Task not awaited

B Compilation error: async Main not supported

C Async Main finished

D No output, program exits immediately

💡 Hint

Modern C# supports async Main returning Task.

Since C# 7.1, async Main returning Task is supported. The program waits 100ms then prints the message.