Why is the main method entry point in most C# programs static?

Question

Why is the main method entry point in most C# programs static?

Floccus

This is a great question, for which there may be no really satisfactory answer. Lots of things run before Main gets called, and these can include as many object constructors as you'd like. But still, I think that if the constructor for the Program object gets an out of memory exception, then your computer is having a really bad day! – Aspen

Because you don't want to frighten C++ and Java programmers too much. – Czerny

Answer 1

In order to call an instance method you need an instance of an object. This means in order to start your program the CLR would need to create an instance of say Program in order to call the method Main. Hence the constructor of Program would run before Main which defeats the purpose of having a main altogether.

Dyestuff

But this means the static constructor is still called? – Eucalyptol

@Yuriy, yes it does. It's specifically called out as such in section 10.11 of the C# language spec. I don't know exactly why this decision was made (may have been forced from the CLR level) – Dyestuff

The purpose of having a main is to have a defined entry point to the application. Defining the entry point as having the framework call new Program().Main(args) instead of the static call wouldn't defeat the purpose at all. – Slavic

The reason is because that's the way java did it. At the time Java was created, it was still assumed that for many jobs Objects could be forgone. You might have a JVM on a chip with no heap (just stack)--where they don't want to (or can't) instantiate a single class. C# was a pretty direct copy of Java at the time even though it's added more enhancements since, but since C# couldn't run in such an environment it would be plausible to have it use a constructor with (args) as a parameter. – Unders

Probably it just didn't occur to the developers that Program() could have the main functionality. – Czerny

@zarawesome: they used to have one or two smart people working at Microsoft. You should substantiate "probably just didn't occur". – Tinkling

@JaredPar: well, I happen to think there still are more than one or two, but the OP seems to have a different opinion. I'm pointing out that, even if the entire company has gone stupid in the last few years, this would have occurred to the one or two they employed back then. – Tinkling

@Yuriy Faktorovich Yes but, aren't staic constructors that are called the first thing to be run during execution? Wouldn't it then make sense for the entry point for a program to be a static constructor? – Meza

If the framework were to always call new Program().Main(args) and, by definition, you have no control over what that Program object is or how it's constructed, is this really any different than Main being static? Which is far simpler, more logical, and easier to implement? Why do I want the language to decide what sort of objects should be instantiated for me? – Abel

Answer 2

I'd turn the question around. What is the compelling benefit of implementing the feature that allows Main to be an instance method? Features are expensive; if there is no compelling benefit, they don't get implemented.

Do you have a really good reason why Main should be allowed to be an instance method?

Gruff

Answer 3

Conceptually you only have one instance of a static. And a static method maps well to the idiom of a single staring point for a program. The language designers could have created a special program class to use with a main method but chose to create a single static function as the entry point. On some levels its really just a design choice.

Haileyhailfellowwellmet

Answer 4

Because otherwise it would have to create an object, and running the constructor could cause negative side effects.

Wise

Answer 5

How could you create your class instance before main otherwise?

Hendley

The same way as you call main. You don't - the runtime does a lot of stuff before main, loading classes and creating objects. – Slavic

Answer 6

Static methods can be executed without creating an instance. By convention, they have the main method as the default method to call.

Fleet

Answer 7

The .NET runtime calls the Main method. (Note: Main may also be called from elsewhere, e.g. from the code Main() in another method of ExampleClass.) The static keyword makes the method accessible without an instance of ExampleClass. So Main method is an entry point and must be declared static.

Otherwise, the program would require an instance, but any instance would require a program.

To avoid that irresolvable circular dependency main is used as an entry point

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reference : http://en.wikipedia.org/wiki/C_Sharp_(programming_language

Myrtamyrtaceous

Answer 8

for every objects of a class contains main method and other methods and variables , there are separate copies of each variable and methods contained by all objects but a main class copy is only one between them and so to make a copy between number of objects we have to make main method as static.

Hydrops