C# Program to Find Average of Numbers

To find the average of numbers in C#, sum all numbers using sum += number and then divide by the count using average = sum / count.

Examples

Inputnumbers = [5]

OutputAverage is 5

Inputnumbers = [2, 4, 6, 8]

OutputAverage is 5

Inputnumbers = [0, 0, 0, 0]

OutputAverage is 0

How to Think About It

To find the average, first add all the numbers together to get a total sum. Then count how many numbers there are. Finally, divide the total sum by the count to get the average value.

Algorithm

1

Get the list of numbers

2

Add all numbers to find the total sum

3

Count how many numbers are in the list

4

Divide the total sum by the count to get the average

5

Display the average

Code

csharp

using System;

class Program {
    static void Main() {
        int[] numbers = {2, 4, 6, 8};
        int sum = 0;
        foreach (int num in numbers) {
            sum += num;
        }
        double average = (double)sum / numbers.Length;
        Console.WriteLine("Average is " + average);
    }
}

Output

Average is 5

Dry Run

Let's trace the example numbers = [2, 4, 6, 8] through the code

1

Initialize sum

sum = 0

2

Add first number

sum = 0 + 2 = 2

3

Add second number

sum = 2 + 4 = 6

4

Add third number

sum = 6 + 6 = 12

5

Add fourth number

sum = 12 + 8 = 20

6

Calculate average

average = 20 / 4 = 5

7

Print result

Output: Average is 5

Iteration	Number Added	Sum After Addition
1	2	2
2	4	6
3	6	12
4	8	20

Why This Works

Step 1: Summing numbers

We use sum += number to add each number to the total sum.

Step 2: Counting numbers

We find how many numbers there are using numbers.Length.

Step 3: Calculating average

We divide the total sum by the count with average = (double)sum / numbers.Length to get the average as a decimal.

Alternative Approaches

Using LINQ Average() method

csharp

using System;
using System.Linq;

class Program {
    static void Main() {
        int[] numbers = {2, 4, 6, 8};
        double average = numbers.Average();
        Console.WriteLine("Average is " + average);
    }
}

This method is shorter and uses built-in LINQ but requires <code>using System.Linq;</code>.

Using for loop instead of foreach

csharp

using System;

class Program {
    static void Main() {
        int[] numbers = {2, 4, 6, 8};
        int sum = 0;
        for (int i = 0; i < numbers.Length; i++) {
            sum += numbers[i];
        }
        double average = (double)sum / numbers.Length;
        Console.WriteLine("Average is " + average);
    }
}

This uses a classic for loop instead of foreach, useful if you need the index.

Complexity: O(n) time, O(1) space

Time Complexity

The program loops through all numbers once to sum them, so time grows linearly with input size.

Space Complexity

Only a few variables are used regardless of input size, so space is constant.

Which Approach is Fastest?

Using LINQ's Average() is concise but internally also loops once, so performance is similar to manual sum and divide.

Approach	Time	Space	Best For
Manual sum with foreach	O(n)	O(1)	Clear step-by-step control
LINQ Average()	O(n)	O(1)	Concise and readable code
For loop sum	O(n)	O(1)	When index access is needed