C# 0 The Complete Reference

house1

 and 

house2

 refer to separate and distinct objects, 

but this is not the case. Instead, 

house1

 and 

house2

 will both refer to the 

same

 object. The 

assignment of 

house1

 to 

house2

 simply makes 

house2

 refer to the same object that 

house1

does. Thus, the object can be acted upon by either 

house1

 or 

house2

. For example, after the 

assignment

house1.Area = 2600;

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P a r t   I :  

T h e   C #   L a n g u a g e

executes, both of these 

WriteLine( )

 statements

Console.WriteLine(house1.Area);

Console.WriteLine(house2.Area);

display the same value: 2600.

Although

house1

 and 

house2

 both refer to the same object, they are not linked in any 

other way. For example, a subsequent assignment to 

house2

 simply changes what object 

house2

 refers to. For example:

Building house1 = new Building();

Building house2 = house1;

Building house3 = new Building();

house2 = house3; // now house2 and house3 refer to the same object.

After this sequence executes, 

house2

 refers to the same object as 

house3

. The object referred 

to by

 house1

 is unchanged.

Methods

As explained, instance variables and methods are two of the primary constituents of classes. 

So far, the 

Building

 class contains data, but no methods. Although data-only classes are 

perfectly valid, most classes will have methods. 

Methods

 are subroutines that manipulate 

the data defined by the class and, in many cases, provide access to that data. Typically, other 

parts of your program will interact with a class through its methods.

A method contains one or more statements. In well-written C# code, each method 

performs only one task. Each method has a name, and it is this name that is used to call 

the method. In general, you can name a method using any valid identifier that you please. 

However, remember that 

Main( )

 is reserved for the method that begins execution of your 

program. Also, don’t use C#’s keywords for method names.

When denoting methods in text, this book has used and will continue to use a 

convention that has become common when writing about C#. A method will have 

parentheses after its name. For example, if a method’s name is 

GetVal

, then it will be 

written

GetVal( )

 when its name is used in a sentence. This notation will help you 

distinguish variable names from method names in this book.

The general form of a method is shown here:

access ret-type name

(

parameter

-

list

) {

    // body of method

}

Here, 

access

 is an access modifier that governs what other parts of your program can call the 

method. As explained earlier, the access modifier is optional. If not present, then the method 

is private to the class in which it is declared. For now, we will declare methods as 

public

 so 

that they can be called by any other code in the program. The 

ret

-

type

 specifies the type of 

data returned by the method. This can be any valid type, including class types that you 

create. If the method does not return a value, its return type must be 

void

. The name of the 

method is specified by 

name.

 This can be any legal identifier other than those that would 

cause conflicts within the current declaration space. The 

parameter-list

is a sequence of type 

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