Chapter 12. Arrays
Arrays in C# is a more complex topic than in Java. Java has only one category of multi-dimensional array. C# groups multi-dimensional arrays into two distinct categories: 'normal' rectangular arrays, and jagged arrays (see Figure 12.1). Things can be a bit confusing because you can view a Java multi-dimensional array as in either category, though I personally think that it fits a little better into 'rectangular arrays'.
Figure 12.1. The different types of arrays in C#.
We will start with the simplest, one dimensional (1D) arrays. Then rectangular multi-dimensional arrays will be covered followed by the more complex jagged multi-dimensional arrays. I shall limit my discussion to 2D arrays for the sections on multi-dimensional arrays – you can extend the idea to n-levels once you have understood the discussion. This chapter ends with some suggestions on how rectangular and jagged arrays can be used together.
I will discuss some general characteristics of arrays in C# first.
Like Java
Arrays are objects in C#. All arrays are subclasses of System.Array in C#. [1]
[1] In Java, array objects are direct subclasses of java.lang.Object.
An array's index starts from 0.
You cannot access beyond the allocated size of an array. If a 1D array has been declared with a size of 6, attempting to access the array through ArrayName[6] or ArrayName[-1] will cause a runtime exception to be thrown. [2]
[2] The exception thrown in System.IndexArrayOutOfRangeException – the equivalent of Java's java.lang.ArrayIndexOutOfBoundsException. Accessing beyond an array's range is allowed in C/C++, where the array boundaries are not checked during runtime.
Unlike Java
The syntax for declaring arrays is different in C#. This will be elaborated on in the next few sections.
Be careful here – the Length property of an array in C# gives the total size of an array. For a multi-dimensional array, it gives the total size of the whole array, instead of just the size of the 'first-level array'. An example will be provided to illustrate this in section 12.2.
Additional note
C# comes with a new useful looping keyword, foreach, which is very convenient for looping through an array (see section 11.1).