The C# Array in C#.NET

Generation Code 39 Full ASCII in C#.NET The C# Array

Variables that contain single values are plenty useful Even class structures that can describe compound objects made up of parts (such as a vehicle with its engine and transmission) are critical But you also need a construct for holding a bunch of objects, such as Bill Gates extensive collection of

vintage cars or a certain author s vintage sock collection The built-in class Array is a structure that can contain a series of elements of the same type (all int values and all double values, for example, or all Vehicle objects and Motor objects you meet these latter sorts of objects in 7 of this minibook)

Consider the problem of averaging a set of six floating-point numbers Each of the six numbers requires its own double storage:

double double double double double double d0 d1 d2 d3 d4 d5 = = = = = = 5; 2; 7; 35; 65; 8;

(Averaging int variables can result in rounding errors, as described in 2 of this minibook) Computing the average of those variables might look like this:

double sum = d0 + d1 + d2 + d3 + d4 + d5; double average = sum / 6;

Listing each element by name is tedious Okay, maybe it s not so tedious when you have only 6 numbers to average, but imagine averaging 600 (or even 6 million) floating-point values

Fortunately, you don t need to name each element separately C# provides the array structure that can store a sequence of values Using an array, you can put all your doubles into one variable, like this:

double[] doublesArray = {5, 2, 7, 35, 65, 8, 1, 9, 1, 3};

You can also declare an empty array without initializing it:

double[] doublesArray = new double[6];

This line allocates space for six doubles but doesn t initialize them The Array class, on which all C# arrays are based, provides a special syntax that makes it more convenient to use The paired brackets [] refer to the way you access individual elements in the array:

doublesArray[0] // Corresponds to d0 (that is, 5) doublesArray[1] // Corresponds to d1 (that is, 2)

The 0th element of the array corresponds to d0, the 1th element to d1, the 2th element to d2, and so on Programmers commonly refer to the 0th element as doublesArray sub-0, to the first element as doublesArray sub-1, and so on The array s element numbers 0, 1, 2, are known as the index In C#, the array index starts at 0 and not at 1 Therefore, you typically don t refer to the element at index 1 as the first element but, rather, as the oneth element or the element at index 1 The first element is the zeroth element If you insist on using normal speech, just be aware that the first element is always at index 0 and the second element is at index 1 The doublesArray variable wouldn t be much of an improvement, were it not for the possibility that the index of the array is a variable Using a for loop is easier than writing out each element by hand, as this program demonstrates:

// FixedArrayAverage -- Average a fixed array of numbers using a loop namespace FixedArrayAverage { using System; public class Program { public static void Main(string[] args) { double[] doublesArray = {5, 2, 7, 35, 65, 8, 1, 9, 1, 3}; // Accumulate the values in the array into the variable sum double sum = 0; for (int i = 0; i < 10; i++) { sum = sum + doublesArray[i]; } // Now calculate the average double average = sum / 10; ConsoleWriteLine(average); ConsoleWriteLine( Press Enter to terminate ); ConsoleRead(); } } }