Programming C#, Second Edition

Variables and Constants

A variable is a storage location with a type. In the preceding examples, both x and y are variables. Variables can have values assigned to them, and those values can be changed programmatically.

WriteLine( )

The .NET Framework provides a useful method for writing output to the screen. The details of this method, System.Console.WriteLine( ), will become clearer as we progress through the book, but the fundamentals are straightforward. Call the method as shown in Example 3-1, passing in a string that you want printed to the console (the screen) and, optionally, parameters that will be substituted. In the following example:

System.Console.WriteLine("After assignment, myInt: {0}", myInt);

the string "After assignment, myInt:" is printed as is, followed by the value in the variable myInt. The location of the substitution parameter {0} specifies where the value of the first output variable, myInt, will be displayed -- in this case at the end of the string. We see a great deal more about WriteLine( ) in coming chapters.

Create a variable by declaring its type and then giving it a name. You can initialize the variable when you declare it, and you can assign a new value to that variable at any time, changing the value held in the variable. This is illustrated in Example 3-1.

Example 3-1. Initializing and assigning a value to a variable

class Values
{
   static void Main( )
   {
      int myInt = 7;
      System.Console.WriteLine("Initialized, myInt: {0}", 
         myInt); 
      myInt = 5; System.Console.WriteLine("After ...