C# Arrays

An array is a collection of similar types of data. For example,

Suppose we need to record the age of 5 students. Instead of creating 5 separate variables, we can simply create an array:

1. C# Array Declaration

In C#, here is how we can declare an array.

datatype[] arrayName;

Here,

• dataType - data type like int, string, char, etc
• arrayName - it is an identifier

Let's see an example,

int[] age;

Here, we have created an array named age. It can store elements of int type.

But how many elements can it store?

To define the number of elements that an array can hold, we have to allocate memory for the array in C#. For example,

// declare an array
int[] age;

// allocate memory for array
age = new int[5];

Here, new int[5] represents that the array can store 5 elements. We can also say the size/length of the array is 5.

int[] age = new int[5];

2. Array initialization in C#

In C#, we can initialize an array during the declaration. For example,

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

Here, we have created an array named numbers and initialized it with values 1, 2, 3, 4, and 5 inside the curly braces.

Note that we have not provided the size of the array. In this case, the C# automatically specifies the size by counting the number of elements in the array (i.e. 5).

In an array, we use an index number to determine the position of each array element. We can use the index number to initialize an array in C#. For example,

// declare an array
int[] age = new int[5];

//initializing array
age[0] = 12;
age[1] = 4;
age[2] = 5;
...

3. Access Array Elements

We can access the elements in the array using the index of the array. For example,

// access element at index 2
array[2];

// access element at index 4
array[4];

Here,

• array[2] - access the 3rd element
• array[4] - access the 5th element

Example: C# Array

using System;

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

      // create an array
      int[] numbers = {1, 2, 3};

      //access first element
      Console.WriteLine("Element in first index : " + numbers[0]);

      //access second element
      Console.WriteLine("Element in second index : " + numbers[1]);

      //access third element
      Console.WriteLine("Element in third index : " + numbers[2]);

      Console.ReadLine();

    }
  }
}

Output

Element in first index : 1
Element in second index : 2
Element in third index : 3

In the above example, we have created an array named numbers with elements 1, 2, 3. Here, we are using the index number to access elements of the array.

• numbers[0] - access first element, 1
• numbers[1] - access second element, 2
• numbers[3] - access third element, 3

4. Change Array Elements

We can also change the elements of an array. To change the element, we simply assign a new value to that particular index. For example,

using System;

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

      // create an array
      int[] numbers = {1, 2, 3};

      Console.WriteLine("Old Value at index 0: " + numbers[0]);

      // change the value at index 0
      numbers[0] = 11;

      //print new value
      Console.WriteLine("New Value at index 0: " + numbers[0]);

      Console.ReadLine();
    }
  }
}

Output

Old Value at index 0: 1
New Value at index 0: 11

In the above example, the initial value at index 0 is 1. Notice the line,

//change the value at index 0
numbers[0] = 11;

Here, we are assigning a new value of 11 to the index 0. Now, the value at index 0 is changed from 1 to 11.

5. Iterating C# Array using Loops

In C#, we can use loops to iterate through each element of an array. For example,

Example: Using for loop

using System;

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

      int[] numbers = { 1, 2, 3};
 	 
      for(int i=0; i < numbers.Length; i++) {
        Console.WriteLine("Element in index " + i + ": " + numbers[i]);
      }

      Console.ReadLine();
    }
  }
}

Output

Element in index 0: 1
Element in index 1: 2
Element in index 2: 3

In the above example, we have used a for loop to iterate through the elements of the array, numbers. Notice the line,

numbers.Length

Here, the Length property of the array gives the size of the array.

We can also use a foreach loop to iterate through the elements of an array. For example,

Example: Using foreach loop

using System;

namespace AccessArrayForeach {
  class Program {
    static void Main(string[] args) {
      int[] numbers = {1, 2, 3};

      Console.WriteLine("Array Elements: ");

      foreach(int num in numbers) {
        Console.WriteLine(num);
      }

      Console.ReadLine();
    }
  }
}

Output

Array Elements:
1
2
3

6. C# Array Operations using System.Linq

In C#, we have the System.Linq namespace that provides different methods to perform various operations in an array. For example,

Example: Find Minimum and Maximum Element

using System;

 // provides us various methods to use in an array
using System.Linq;

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

      int[] numbers = {51, 1, 3, 4, 98};

      // get the minimum element
      Console.WriteLine("Smallest  Element: " + numbers.Min());  

      // Max() returns the largest number in array
      Console.WriteLine("Largest Element: " + numbers.Max());  
 	 
      Console.ReadLine();
    }
  }
}

Output

Smallest Element: 1
Largest Element: 98

In the above example,

• numbers.Min() - returns the smallest number in an array, 1
• numbers.Max() - returns the largest number in an array, 98

Example: Find the Average of an Array

using System;
// provides us various methods to use in an array
using System.Linq;

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

      int[] numbers = {30, 31, 94, 86, 55};
 	 
      // get the sum of all array elements
      float sum = numbers.Sum();
 	 
      // get the total number of elements present in the array
      int count = numbers.Count();
 	 
      float average = sum/count;

      Console.WriteLine("Average : " + average);
 	
      // compute the average
      Console.WriteLine("Average using Average() : " + numbers.Average());
 	 
      Console.ReadLine();
    }
  }
}

Output

Average : 59.2
Average using Average() : 59.2

In the above example, we have used

• numbers.Sum() to get the sum of all the elements of the array
• numbers.Count() to get the total number of element present inside the array

We then divide the sum by count to get the average.

float average = sum / count;

Here, we have also used the numbers.Average() method of the System.Linq namespace to get the average directly.

Note: It is compulsory to use the System.Linq namespace while using Min(), Max(), Sum(), Count(), and Average() methods.