C# Multidimensional Array

In this tutorial, we will learn about the multidimensional array in C# using the example of two-dimensional array.

In a multidimensional array, each element of the array is also an array. For example,

int[ , ] x = { { 1, 2 ,3}, { 3, 4, 5 } };

Here, x is a multidimensional array which has two elements: {1, 2, 3} and {3, 4, 5}. And, each element of the array is also an array with 3 elements.

A 2-dimensional array can be thought of as a table, which has x number of rows and y number of columns. Following is a 2-dimensional array, which contains 3 rows and 4 columns −

Thus, every element in the array a is identified by an element name of the form a[ i , j ], where a is the name of the array, and i and j are the subscripts that uniquely identify each element in array a.

Two-Dimensional Array Declaration

Here's how we declare a 2D array in C#.

int[ , ] x = new int [3, 4];

Initializing Two-Dimensional Arrays

Multidimensional arrays may be initialized by specifying bracketed values for each row. The Following array is with 3 rows and each row has 4 columns.

int [,] a = new int [3,4] {
   {0, 1, 2, 3} ,   /*  initializers for row indexed by 0 */
   {4, 5, 6, 7} ,   /*  initializers for row indexed by 1 */
   {8, 9, 10, 11}   /*  initializers for row indexed by 2 */
};

Accessing Two-Dimensional Array Elements

An element in 2-dimensional array is accessed by using the subscripts. That is, row index and column index of the array. For example,

int[,] arr2d = new int[3,2]{ 

                                {1, 2}, 
                                {3, 4}, 
                                {5, 6} 
                            };

arr2d[0, 0]; //returns 1
arr2d[0, 1]; //returns 2
arr2d[1, 0]; //returns 3
arr2d[1, 1]; //returns 4
arr2d[2, 0]; //returns 5
arr2d[2, 1]; //returns 6
//arr2d[3, 0]; //throws run-time error as there is no 4th row

In the above example, the value of a two-dimensional array can 

be accessed by index no of row and column as [row index, column index].

So, [0, 0] returns the value of the first row and first column and [1, 1] returns the value from the second row and second column.

Change Array Elements

We can also change the elements of a two-dimensional array. To change the element, we simply assign a new value to that particular index. For example,
using System;

namespace MultiDArray {
  class Program {
    static void Main(string[] args) {

    int[ , ] numbers = {{2, 3}, {4, 5}};
 	 
     // old element
    Console.WriteLine("Old element at index [0, 0] : "+numbers[0, 0]);
 	 
      // assigning new value
    numbers[0, 0] = 222;
  	 
      // new element
    Console.WriteLine("New element at index [0, 0] : "+numbers[0, 0]);
    }
  }
}
Output
Old element at index [0, 0] : 2
New element at index [0, 0] : 222
In the above example, the initial value at index [0, 0] is 2. Notice the line,
// assigning new value
numbers[0, 0] = 222;
Here, we are assigning a new value 222 at index [0, 0]. Now, the value at index [0, 0] is changed from 2 to 222.
Iterating C# Array using Loop
using System;

namespace MultiDArray {
  class Program  {
    static void Main(string[] args)  {

      int[ , ] numbers = { {2, 3, 9}, {4, 5, 9} };
   	 
      for(int i = 0; i < numbers.GetLength(0); i++)  { 
        Console.Write("Row "+ i+": ");

        for(int j = 0; j < numbers.GetLength(1); j++)  { 
          Console.Write(numbers[i, j]+" ");
 
        }
        Console.WriteLine(); 
  
      }  
    }
  }
}
Output
Row 0: 2 3 9
Row 1: 4 5 9
In the above example, we have used a nested for loop to iterate through the elements of a 2D array. Here,
numbers.GetLength(0) - gives the number of rows in a 2D array
numbers.GetLength(1) - gives the number of elements in the row
Note: We can also create a 3D array. Technically, a 3D array is an array that has multiple two-dimensional arrays as its elements. For example,
int[ , , ] numbers = { { { 1, 3, 5 }, { 2, 4, 6 } },
                                 { { 2, 4, 9 }, { 5, 7, 11 } } };
Here, [ , , ] (2 commas) denotes the 3D array.