C# class without main method

Question

I'm learning C# and I'm very new to it, so forgive me for the seemingly stupid question. I have some experience in Java, and I noticed that C# programs also need a main() method in their main class.

What if I want to create a class that isn't a main class, i.e. one that I import into a main class?

I tried to do that, and when I compile (via cmd using csc File.cs) the compiler says that the .exe that it will make has no main() method. Does that mean that I was wrong, and every class needs a main() method, or that I'm compiling it wrongly?

Maybe the problem's in the code (since I'm relying on my knowledge of Java syntax), which looks like this:

public class Class
{
    int stuff;
    public Class(int stuff)
    {
        this.stuff = stuff;
        stuff();
    }
    public void method()
    {
        stuff();
    }
}

EDIT: I'm afraid this is terribly misunderstood. I'm not asking if the file needs a main method, I'm asking how I can import this class into another class, because I realise that if I am to do this I can't have a main (as I said, I have some Java experience), but whenever I try to compile without one the compiler tells me that I need one.

Answer 1

##Not all classes need `Main` method.

As MSDN States

The Main method is the entry point of a C# console application or windows application. (Libraries and services do not require a Main method as an entry point.). When the application is started, the Main method is the first method that is invoked.

There can only be one entry point in a C# program. If you have more than one class that has a Main method, you must compile your program with the /main compiler option to specify which Main method to use as the entry point.

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Only one class need to keep the Main method, the class which acts as entry point of the application.

The signature of the main method is : static void Main(string[] args) or static void Main() or static int Main(string[] args) or static int Main()

Check out this link for more details : Main() and Command-Line Arguments (C# Programming Guide)

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For your above example:

public class MyClassName // changed the class name, avoid using the reserved keyword :P
{
    int stuff;
    public MyClassName(int stuff)  // is the constructor
    {
        this.stuff = stuff;
    }
    public void method()
    {
        stuff = 1;
    }
}

If you need to use that class, you can create a static class with main method:

class ProgramEntry
{
    static void Main(string[] args)
    {
        MyClassName classInstance = new MyClassName(2);
        classInstance.method();
    }
}

---

Starting C# 9 the option to have a program without the Main method has been introduced. Instead of having to declare the Main method, you can now write code directly in a file outside of a class. For more details see Top-level statements - programs without Main methods.

Answer 2

In this scenario you need at least one class in your code with the Main method in it. The other classes do not need the Main method.