C# 4 and .NET 4

26 ❘ ChaPTer 2 cOre c#
All C# code must be contained within a class. The class declaration consists of the class keyword, followed
by the class name and a pair of curly braces. All code associated with the class should be placed between
these braces.
Next, you declare a method called Main(). Every C# executable (such as console applications, Windows
applications, and Windows services) must have an entry point — the Main() method (note the capital M):
public static void Main()
{
The method is called when the program is started. This method must return either nothing (void) or an
integer (int). Note the format of method definitions in C#:
[modifiers] return_type MethodName([parameters])
{
// Method body. NB. This code block is pseudo-code.
}
Here, the first square brackets represent certain optional keywords. Modifiers are used to specify certain
features of the method you are defining, such as where the method can be called from. In this case, you
have two modifiers: public and static. The public modifier means that the method can be accessed from
anywhere, so it can be called from outside your class. The static modifier indicates that the method does
not operate on a specific instance of your class and therefore is called without first instantiating the class.
This is important because you are creating an executable rather than a class library. You set the return type
to void, and in the example, you don’t include any parameters.
Finally, we come to the code statements themselves:
Console.WriteLine("Hello from Wrox.");
Console.ReadLine();
return;
In this case, you simply call the WriteLine() method of the System.Console class to write a line of text to
the console window. WriteLine() is a static method, so you don’t need to instantiate a Console object
before calling it.
Console.ReadLine() reads user input. Adding this line forces the application to wait for the carriage
return key to be pressed before the application exits, and, in the case of Visual Studio 2010, the console
window disappears.
You then call return to exit from the method (also, because this is the Main() method, you exit the
program as well). You specified void in your method header, so you don’t return any values.
Now that you have had a taste of basic C# syntax, you are ready for more detail. Because it is virtually
impossible to write any nontrivial program without variables, we will start by looking at variables in C#.
Variables
You declare variables in C# using the following syntax:
datatype identifier;
For example:
int i;
This statement declares an int named i. The compiler won’t actually let you use this variable in an
expression until you have initialized it with a value.
After it has been declared, you can assign a value to the variable using the assignment operator, =:
i = 10;
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