An array is a group of variables (called elements) containing values that all have the same type. Recall that types are divided into two categoriesvalue types and reference types. Arrays are reference types. As you will see, what we typically think of as an array is actually a reference to an array instance in memory. The elements of an array can be either value types or reference types (including other arrays, as we will see in Section 8.10). To refer to a particular element in an array, we specify the name of the reference to the array and the position number of the element in the array. The position number of the element is called the element's index.

Figure 8.1 shows a logical representation of an integer array called c. This array contains 12 elements. An application refers to any one of these elements with an array-access expression that includes the name of the array, followed by the index of the particular element in square brackets ([]). The first element in every array has index zero and is sometimes called the zeroth element. Thus, the elements of array c are c[ 0 ], c[ 1 ], c[ 2 ] and so on. The highest index in array c is 11, which is one less than the number of elements in the array, because indices begin at 0. Array names follow the same conventions as other variable names.

Figure 8.1. A 12-element array.

An index must be a nonnegative integer and can be an expression. For example, if we assume that variable a is 5 and variable b is 6, then the statement

c[ a + b ] += 2;

adds 2 to array element c[ 11 ]. Note that an indexed array name is an array-access expression. Such expressions can be used on the left side of an assignment to place a new value into an array element. The array index must be a value of type int, uint, long or ulong, or a value of a type that can be implicitly promoted to one of these types.

Let's examine array c in Fig. 8.1 more closely. The name of the array is c. Every array instance knows its own length and provides access to this information with the Length property. For example, the expression c.Length uses array c's Length property to determine the length of the array. Note that the Length property of an array cannot be changed, because it does not provide a set accessor. The array's 12 elements are referred to as c[ 0 ], c[ 1 ], c[ 2 ], ..., c[ 11 ]. It is an error to refer to elements outside of this range, such as c[ -1 ] or c[ 12 ]. The value of c[ 0 ] is -45, the value of c[ 1 ] is 6, the value of c[ 2 ] is 0, the value of c[ 7 ] is 62 and the value of c[ 11 ] is 78. To calculate the sum of the values contained in the first three elements of array c and store the result in variable sum, we would write

sum = c[ 0 ] + c[ 1 ] + c[ 2 ];

To divide the value of c[ 6 ] by 2 and assign the result to the variable x, we would write

x = c[ 6 ] / 2;



    Introduction to Computers, the Internet and Visual C#

    Introduction to the Visual C# 2005 Express Edition IDE

    Introduction to C# Applications

    Introduction to Classes and Objects

    Control Statements: Part 1

    Control Statements: Part 2

    Methods: A Deeper Look


    Classes and Objects: A Deeper Look

    Object-Oriented Programming: Inheritance

    Polymorphism, Interfaces & Operator Overloading

    Exception Handling

    Graphical User Interface Concepts: Part 1

    Graphical User Interface Concepts: Part 2


    Strings, Characters and Regular Expressions

    Graphics and Multimedia

    Files and Streams

    Extensible Markup Language (XML)

    Database, SQL and ADO.NET

    ASP.NET 2.0, Web Forms and Web Controls

    Web Services

    Networking: Streams-Based Sockets and Datagrams

    Searching and Sorting

    Data Structures



    Appendix A. Operator Precedence Chart

    Appendix B. Number Systems

    Appendix C. Using the Visual Studio 2005 Debugger

    Appendix D. ASCII Character Set

    Appendix E. Unicode®

    Appendix F. Introduction to XHTML: Part 1

    Appendix G. Introduction to XHTML: Part 2

    Appendix H. HTML/XHTML Special Characters

    Appendix I. HTML/XHTML Colors

    Appendix J. ATM Case Study Code

    Appendix K. UML 2: Additional Diagram Types

    Appendix L. Simple Types


    Visual C# How to Program
    Visual C# 2005 How to Program (2nd Edition)
    ISBN: 0131525239
    EAN: 2147483647
    Year: 2004
    Pages: 600 © 2008-2020.
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