Declaring - Fixed Size

Numbers can be grouped together into arrays to represent both matrices and vectors
These can be represented by using an Array data structure.

A single-dimensional array of objects is declared like this:
type[] arrayName;

int[] array = new int[5]; 
int[] array1 = new int[] { 1, 3, 5, 7, 9 }; 
int[] array2 = {1, 3, 5, 7, 9}; 
string[] days = {"Sun", "Mon", "Tue", "Wed", "Thr", "Fri", "Sat"}; 

The default value of numeric array elements is zero
The default value of any reference elements is null

Fixed Size Arrays

In C# the number inside the bracket represents the number of items in the array

int[] myArray1 = new int[3] { 1, 2, 3 }; 

int[] myArray2 = new int[] { 1, 2, 3 }; 

int[] myArray3 = { 1, 2, 3 }; 

var myArray4 = new[] {1, 2, 3};               // implicitly typed, inferred from items 

System.Array myArray5 = System.Array.CreateInstance(typeof(System.Int32), 3); 

When isize = 5, there are 5 elements, myArray(0) to myArray(4).

long[] myArray = new long[5]; 

int isize = 5; 
long[] myArray = new long[isize]; 

long[] myArray = new long[3]; 
myArray[0] = 5; 
myArray[1] = 10; 
myArray.SetValue(15,2); 

Not Zero Based

//1 dimensional - zero based 
System.Array i2 = Array.CreateInstance(typeof(int), new int[] { 2 }, new int[] { 100 }); 

//1 dimensional - non zero based 
System.Array myArray = Array.CreateInstance(typeof(double), new int[1] { 12 }, new int[1] { 1 }); 

Declaration and creation can be done in 2 steps or combined into 1 line
Values can be intialised or left as the defaults