How to access elements from a rectangular array in C#?

To access elements from a rectangular array in C#, you need to specify the row and column indices using square brackets. Multi-dimensional arrays are also called rectangular arrays because they form a rectangular structure with fixed dimensions.

Syntax

Following is the syntax for accessing elements in a rectangular array −

dataType[,] arrayName = new dataType[rows, columns];
arrayName[rowIndex, columnIndex] = value;

To retrieve an element −

dataType element = arrayName[rowIndex, columnIndex];

Using Basic Element Access

Example

using System;

class Program {
   static void Main(string[] args) {
      int[,] a = new int[3, 3];
      a[0,0] = 10;
      a[0,1] = 20;
      a[0,2] = 30;
      a[1,0] = 40;
      a[1,1] = 50;
      a[1,2] = 60;
      a[2,0] = 70;
      a[2,1] = 80;
      a[2,2] = 90;

      // Accessing specific elements
      int element1 = a[0,1];  // Second element in first row
      int element2 = a[2,2];  // Last element
      
      Console.WriteLine("Element at [0,1]: " + element1);
      Console.WriteLine("Element at [2,2]: " + element2);
      
      // Display all elements
      Console.WriteLine("\nAll elements:");
      for (int i = 0; i < 3; i++) {
         for (int j = 0; j < 3; j++) {
            Console.WriteLine("a[{0},{1}] = {2}", i, j, a[i,j]);
         }
      }
   }
}

The output of the above code is −

Element at [0,1]: 20
Element at [2,2]: 90

All elements:
a[0,0] = 10
a[0,1] = 20
a[0,2] = 30
a[1,0] = 40
a[1,1] = 50
a[1,2] = 60
a[2,0] = 70
a[2,1] = 80
a[2,2] = 90

Using Array Initialization

Example

using System;

class Program {
   static void Main(string[] args) {
      // Initialize array with values directly
      int[,] numbers = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
      
      // Access diagonal elements
      Console.WriteLine("Diagonal elements:");
      for (int i = 0; i < 3; i++) {
         Console.WriteLine("numbers[{0},{1}] = {2}", i, i, numbers[i,i]);
      }
      
      // Access elements in second column
      Console.WriteLine("\nSecond column elements:");
      for (int i = 0; i < 3; i++) {
         Console.WriteLine("numbers[{0},{1}] = {2}", i, 1, numbers[i,1]);
      }
   }
}

The output of the above code is −

Diagonal elements:
numbers[0,0] = 1
numbers[1,1] = 5
numbers[2,2] = 9

Second column elements:
numbers[0,1] = 2
numbers[1,1] = 5
numbers[2,1] = 8

Common Access Patterns

Conclusion

Accessing elements in rectangular arrays requires specifying both row and column indices using the format array[row, column]. You can access individual elements, entire rows, columns, or follow specific patterns like diagonals using appropriate loop structures.