C# Array Initialization on []

Question

So in C# you can define an array like so:

string[] Demo;
string[,] Demo;
string[,,] Demo;

What does the , represent?

Answer 1

The dimensions.

• No comma: 1 dimension
• 1 comma: 2 dimensions
• 2 commas: 3 dimensions
• and so on...

Learn more about multi-dimensional arrays on MSDN .

Answer 2

Multi-dimensional arrays.

The following example would declare a string array with two dimensions:

string[,] demo = new string[5, 3];

The [,] syntax is useful, for example, if you have a method taking a 2D array as a parameter:

void myMethod(string[,] some2Darray) { ... }

Note the difference between multi-dimensional arrays (eg string[,] ), which are like a matrix :

+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+

and jagged arrays (eg string[][] ), which are basically arrays of arrays:

+------------+
| +-+-+-+-+  |
| | | | | |  |
| +-+-+-+-+  |
+------------+
| +-+-+-+-+  |
| | | | | |  |
| +-+-+-+-+  |
+------------+
| +-+-+-+    |
| | | | |    |  <- possible in jagged arrays but not in multi-dimensional arrays
| +-+-+-+    |
+------------+

Reference:

• Arrays (C# Programming Guide)

Answer 3

These are multi-dimensional arrays .

The difference between this and array[][] as you might be used to is described here and here