Aggregate functions (Count, Sum, Average) in C Sharp (C#) - Mini Project: Build & Apply

Aggregate functions (Count, Sum, Average)

📖 Scenario: You work in a small store and want to analyze sales data to understand how many items were sold, the total sales amount, and the average price per item.

🎯 Goal: Build a simple C# program that uses aggregate functions to count items, sum prices, and calculate the average price from a list of sales.

📋 What You'll Learn

Create a list of sales with exact prices

Create a variable to hold the number of sales

Calculate the total sum of sales prices

Calculate the average price of sales

Print the count, sum, and average values

💡 Why This Matters

🌍 Real World

Stores and businesses often analyze sales data to understand performance and make decisions.

💼 Career

Knowing how to use aggregate functions like count, sum, and average is essential for data analysis and reporting in many programming jobs.

1

Create the sales data list

Create a List<double> called sales with these exact values: 10.5, 20.0, 15.75, 30.0, 25.25.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Create the sales list with exact values
        // Your code here
    }
}

Need a hint?

Use List<double> and initialize it with the exact numbers inside curly braces.

2

Create a variable to count sales

Create an int variable called count and set it to the number of items in the sales list using sales.Count.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List sales = new List { 10.5, 20.0, 15.75, 30.0, 25.25 };
        // Create an int variable count and set it to sales.Count
        // Your code here
    }
}

Need a hint?

Use int count = sales.Count; to get the number of items.

3

Calculate sum and average of sales

Create a double variable called sum and set it to the sum of all values in sales using sales.Sum(). Then create a double variable called average and set it to sum / count.

C Sharp (C#)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        List sales = new List { 10.5, 20.0, 15.75, 30.0, 25.25 };
        int count = sales.Count;
        // Calculate sum using sales.Sum()
        // Calculate average as sum / count
        // Your code here
    }
}

Need a hint?

Use sales.Sum() to get the total sum. Then divide by count to get the average.

4

Print the count, sum, and average

Write three Console.WriteLine statements to print the values of count, sum, and average exactly as shown:
Count: 5
Sum: 101.5
Average: 20.3.
Use average.ToString("F1") to format the average to one decimal place.

C Sharp (C#)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        List sales = new List { 10.5, 20.0, 15.75, 30.0, 25.25 };
        int count = sales.Count;
        double sum = sales.Sum();
        double average = sum / count;
        // Print count, sum, and average with formatting
        // Your code here
    }
}

Need a hint?

Use Console.WriteLine with string interpolation and format average with ToString("F1").