Microsoft 9GD00001 manual Main Method

40Microsoft Visual Studio 2010: A Beginner’s Guide

The skeleton code in Listing 2-1 is what VS created when the new Console application was created. It is there to give you a head start on writing your program. What you now have is a whole computer program. This program doesn’t do much of anything at this point, but it will actually run and then end itself. Looking at the whole program, you can see that there are sets of nested curly braces in the C# code. The VB code has Module and Sub with corresponding End identifiers to indicate the boundaries of a block. The braces in C# code always come in pairs and define a block. The following explanation works from the inside out to help you understand what this code means.

The Main Method

The innermost block of the C# code is the static void Main(string[] args) definition, which is called a method. The method in VB is called Sub Main and is identical in purpose. You’ll learn later that methods are one way you can group code into logical chunks of functionality. You can think of methods as actions where you, as the method author, tell the computer what to do. The name of this particular method is Main, which is referred to as the entry point of the program, the place where a Console application first starts running. Another way of thinking about Main is that this is the place your computer first transfers control to your program. Therefore, you would want to put code inside of Main to make your program do what you want it to.

In C#, Main must be capitalized. It’s also important to remember that C# is case- sensitive, meaning that Main (capitalized) is not the same as main (lowercase). Although VS capitalizes your code for you if you forget to, VB is not case-sensitive. Capitalization is a common gotcha, especially for VB programmers learning C#.

In C#, methods can return values, such as numbers, text, or other types of values, and the type of thing they can return is specified by you right before the method name. In VB, a Sub (a shortened keyword derived from the term subroutine) does not return a value, but a Function does, and you’ll see examples soon. Since Main, in the C# example, does not return a value, the return type is replaced with the keyword void. Methods can specify parameters for holding arguments that callers pass to the method. In the case of Main, the parameter is an array of strings, with a variable name of args. The args parameter will hold all of the parameters passed to this program from the command line.

One more part of the C# Main method is the static keyword, which is a modifier that says there will only ever be a single instance of this method for the life of the program. To understand instances, consider that methods are members of object types where an object can be anything in the domain of the application you’re writing, such as a Customer, Account, or Vehicle. Think about a company that has multiple customers. Each customer is a separate instance, which also means that each Customer instance contains methods