Creating an array preinitializes the elements with default values.
The default value for a type is the result of a bitwise zeroing of memory.
| Type | Default value |
|---|---|
| All reference types | null |
| All numeric and enum types | 0 |
| char type | '\0' |
| bool type | false |
The following code creates an array of integers.
It will allocate 1,000 integers with default value 0 for each element
int[] a = new int[1000]; Console.Write (a[123]); // 0 Console.Write (a[124]); // 0 Console.Write (a[999]); // 0
When the element type is a value type, each element value is allocated as part of the array.
For example the following code defines a Point structure:
struct Point {
public int X, Y;
}
When creating an array with 1000 Point structure
Point[] a = new Point[1000]; int x = a[500].X; // 0
Each array element is allocated memory and initialized.
If we defined Point as class, creating the array would have allocated 1,000 null references:
class Point { public int X, Y; } Point[] a = new Point[1000]; int x = a[500].X; // Runtime error, NullReferenceException
To explicitly instantiate 1,000 Points class object after instantiating the array:
Point[] a = new Point[1000]; for (int i = 0; i < a.Length; i++) // Iterate i from 0 to 999 a[i] = new Point(); // Set array element i with new point
An array itself is always a reference type object, regardless of the element type.
For instance, the following is legal:
int[] a = null;