C# program to Loop over a two dimensional array

A two-dimensional array in C# stores elements in a grid format with rows and columns. To loop through all elements, you need to iterate through both dimensions using nested loops.

Syntax

Following is the syntax for declaring a two-dimensional array −

dataType[,] arrayName = new dataType[rows, columns];

Following is the syntax for looping through a two-dimensional array using nested for loops −

for (int i = 0; i <= array.GetUpperBound(0); i++) {
   for (int j = 0; j <= array.GetUpperBound(1); j++) {
      // Access array[i, j]
   }
}

Using GetUpperBound() Method

The GetUpperBound() method returns the highest index of a specified dimension. For a 3x3 array, GetUpperBound(0) returns 2 (rows) and GetUpperBound(1) returns 2 (columns).

Example

using System;

public class Demo {
   public static void Main() {
      string[,] array = new string[3, 3];
      array[0, 0] = "One";
      array[0, 1] = "Two";
      array[0, 2] = "Three";
      array[1, 0] = "Four";
      array[1, 1] = "Five";
      array[1, 2] = "Six";
      array[2, 0] = "Seven";
      array[2, 1] = "Eight";
      array[2, 2] = "Nine";

      // getting upper bound
      int uBound0 = array.GetUpperBound(0);
      int uBound1 = array.GetUpperBound(1);

      for (int i = 0; i <= uBound0; i++) {
         for (int j = 0; j <= uBound1; j++) {
            string res = array[i, j];
            Console.WriteLine(res);
         }
      }
   }
}

The output of the above code is −

One
Two
Three
Four
Five
Six
Seven
Eight
Nine

Using Array Length Property

You can also use the Length property with GetLength() method to determine the size of each dimension −

Example

using System;

public class Demo {
   public static void Main() {
      int[,] numbers = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};

      Console.WriteLine("Array dimensions: " + numbers.GetLength(0) + "x" + numbers.GetLength(1));
      
      for (int i = 0; i < numbers.GetLength(0); i++) {
         for (int j = 0; j < numbers.GetLength(1); j++) {
            Console.Write(numbers[i, j] + " ");
         }
         Console.WriteLine();
      }
   }
}

The output of the above code is −

Array dimensions: 3x3
1 2 3 
4 5 6 
7 8 9 

Using foreach Loop

The foreach loop provides a simpler way to iterate through all elements without managing indices −

Example

using System;

public class Demo {
   public static void Main() {
      string[,] fruits = {{"Apple", "Banana"}, {"Orange", "Grape"}, {"Mango", "Cherry"}};

      Console.WriteLine("Using foreach loop:");
      foreach (string fruit in fruits) {
         Console.WriteLine(fruit);
      }
   }
}

The output of the above code is −

Using foreach loop:
Apple
Banana
Orange
Grape
Mango
Cherry

Comparison of Loop Methods

Conclusion

Looping over two-dimensional arrays in C# can be done using nested for loops with GetUpperBound(), GetLength(), or the simpler foreach loop. Choose the method based on whether you need index access or just the element values.