Managing User Data: Filtering and Aggregation in C#

Welcome to today's lesson on applying data filtering and aggregation in a real-world scenario using a user management system . We'll start by building a foundational structure that can handle basic user operations. Then, we'll expand it by introducing more advanced functionalities that allow filtering and aggregating user data.

Starter Task Methods

In our starter task, we will implement a class that manages basic operations on a collection of user data, specifically handling adding new users, retrieving user profiles, and updating user profiles. Here are the starter task methods: addUser(string userId, int age, string country, bool subscribed) - adds a new user with the specified attributes. Returns true if the user was added successfully and false if a user with the same userId already exists. getUser(string userId) - returns the user's profile as an object if the user exists; otherwise, returns null . updateUser(string userId, int? age, string country, bool? subscribed) - updates the user's profile based on non-null parameters. Returns true if the user exists and was updated, false otherwise.

Starter Task Implementation

The C# implementation of our starter task is shown below: C# using System; using System.Collections.Generic; public class UserManager {private Dictionary<string, UserProfile> users; public UserManager() {users = new Dictionary<string, UserProfile>();} public bool addUser(string userId, int age, string country, bool subscribed) {if (users.ContainsKey(userId)) {return false;} users[userId] = new UserProfile { Age = age, Country = country, Subscribed = subscribed }; return true;} public UserProfile getUser(string userId) {if (users.TryGetValue(userId, out var profile)) {return profile;} return null;} public bool updateUser(string userId, int? age, string country, bool? subscribed) {if (!users.ContainsKey(userId)) {return false;} if (age.HasValue) {users[userId].Age = age.Value;} if (country != null) {users[userId].Country = country;} if (subscribed.HasValue) {users[userId].Subscribed = subscribed.Value;} return true;}} public class UserProfile {public int Age { get; set; } public string Country { get; set; } public bool Subscribed { get; set; }} class Program {static void Main() {var um = new UserManager(); Console.WriteLine(um.addUser("u1", 25, "USA", true)); // true Console.WriteLine(um.addUser("u2", 30, "Canada", false)); // true Console.WriteLine(um.addUser("u1", 22, "Mexico", true)); // false Console.WriteLine(um.getUser("u1")); // UserProfile with specified attributes Console.WriteLine(um.updateUser("u1", 26, null, null)); // true Console.WriteLine(um.updateUser("u3", 19, "UK", false)); // false}} This implementation covers all our starter methods. Let's move forward and introduce more complex functionalities.

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Step 1: Adding filterUsers Method

This method filters users based on the criteria provided. Let's see how it works:

using System;
using System.Collections.Generic;

public class UserManager
{
    // Existing methods...

    // Method to filter users based on criteria
    public List<string> filterUsers(int? minAge, int? maxAge, string country, bool? subscribed)
    {
        var filteredUsers = new List<string>();

        foreach (var kvp in users)
        {
            var userId = kvp.Key;
            var profile = kvp.Value;

            // Check minimum age criterion
            if (minAge.HasValue && profile.Age < minAge)
            {
                continue;
            }
            // Check maximum age criterion
            if (maxAge.HasValue && profile.Age > maxAge)
            {
                continue;
            }
            // Check country criterion
            if (country != null && profile.Country != country)
            {
                continue;
            }
            // Check subscription status criterion
            if (subscribed.HasValue && profile.Subscribed != subscribed)
            {
                continue;
            }
            filteredUsers.Add(userId);
        }
        return filteredUsers;
    }
}

class Program
{
    static void Main()
    {
        var um = new UserManager();
        Console.WriteLine(um.addUser("u1", 25, "USA", true));  // true
        Console.WriteLine(um.addUser("u2", 30, "Canada", false));  // true
        Console.WriteLine(um.addUser("u1", 22, "Mexico", true));  // false
        Console.WriteLine(um.getUser("u1"));  // UserProfile with specified attributes
        Console.WriteLine(um.updateUser("u1", 26, null, null));  // true
        Console.WriteLine(um.updateUser("u3", 19, "UK", false));  // false

        Console.WriteLine(string.Join(", ", um.filterUsers(20, 30, "USA", true)));  // ["u1"]
    }
}

using System;
using System.Collections.Generic;

public class UserManager
{
    // Existing methods...

    // Method to filter users based on criteria
    public List<string> filterUsers(int? minAge, int? maxAge, string country, bool? subscribed)
    {
        var filteredUsers = new List<string>();

        foreach (var kvp in users)
        {
            var userId = kvp.Key;
            var profile = kvp.Value;

            // Check minimum age criterion
            if (minAge.HasValue && profile.Age < minAge)
            {
                continue;
            }
            // Check maximum age criterion
            if (maxAge.HasValue && profile.Age > maxAge)
            {
                continue;
            }
            // Check country criterion
            if (country != null && profile.Country != country)
            {
                continue;
            }
            // Check subscription status criterion
            if (subscribed.HasValue && profile.Subscribed != subscribed)
            {
                continue;
            }
            filteredUsers.Add(userId);
        }
        return filteredUsers;
    }
}

class Program
{
    static void Main()
    {
        var um = new UserManager();
        Console.WriteLine(um.addUser("u1", 25, "USA", true));  // true
        Console.WriteLine(um.addUser("u2", 30, "Canada", false));  // true
        Console.WriteLine(um.addUser("u1", 22, "Mexico", true));  // false
        Console.WriteLine(um.getUser("u1"));  // UserProfile with specified attributes
        Console.WriteLine(um.updateUser("u1", 26, null, null));  // true
        Console.WriteLine(um.updateUser("u3", 19, "UK", false));  // false

        Console.WriteLine(string.Join(", ", um.filterUsers(20, 30, "USA", true)));  // ["u1"]
    }
}

The filterUsers method filters users based on minAge, maxAge, country, and subscribed status criteria.
It iterates over the users dictionary and checks each user's profile against the provided criteria.
Users who meet all the criteria are added to the filteredUsers list, which is then returned.
The example usage shows how to add users and filter them based on different criteria.

Step 2: Adding aggregateStats Method

This method aggregates statistics from the user profiles. Let's implement it:

using System;
using System.Collections.Generic;

public class UserManager
{
    // Existing methods...

    // Method to aggregate statistics from user profiles
    public Stats aggregateStats()
    {
        var totalUsers = users.Count;
        if (totalUsers == 0)
        {
            return new Stats { TotalUsers = 0, AverageAge = 0, SubscribedRatio = 0.00 };
        }

        // Calculate total age by summing ages of all users
        var totalAge = 0;
        var subscribedUsers = 0;
        foreach (var profile in users.Values)
        {
            totalAge += profile.Age;
            if (profile.Subscribed)
            {
                subscribedUsers++;
            }
        }

        // Calculate average age (rounded down)
        var averageAge = totalAge / totalUsers;
        // Calculate subscribed ratio (to two decimals)
        var subscribedRatio = Math.Round((double)subscribedUsers / totalUsers, 2);

        return new Stats { TotalUsers = totalUsers, AverageAge = averageAge, SubscribedRatio = subscribedRatio };
    }
}

public class Stats
{
    public int TotalUsers { get; set; }
    public int AverageAge { get; set; }
    public double SubscribedRatio { get; set; }
}

class Program
{
    static void Main()
    {
        var um = new UserManager();
        Console.WriteLine(um.addUser("u1", 25, "USA", true));  // true
        Console.WriteLine(um.addUser("u2", 30, "Canada", false));  // true
        Console.WriteLine(um.addUser("u1", 22, "Mexico", true));  // false
        Console.WriteLine(um.getUser("u1"));  // UserProfile with specified attributes
        Console.WriteLine(um.updateUser("u1", 26, null, null));  // true
        Console.WriteLine(um.updateUser("u3", 19, "UK", false));  // false

        Console.WriteLine(string.Join(", ", um.filterUsers(20, 30, "USA", true)));  // ["u1"]
        Console.WriteLine(um.aggregateStats().TotalUsers);  // 2
        Console.WriteLine(um.aggregateStats().AverageAge);  // 27
        Console.WriteLine(um.aggregateStats().SubscribedRatio);  // 0.50
    }
}

using System;
using System.Collections.Generic;

public class UserManager
{
    // Existing methods...

    // Method to aggregate statistics from user profiles
    public Stats aggregateStats()
    {
        var totalUsers = users.Count;
        if (totalUsers == 0)
        {
            return new Stats { TotalUsers = 0, AverageAge = 0, SubscribedRatio = 0.00 };
        }

        // Calculate total age by summing ages of all users
        var totalAge = 0;
        var subscribedUsers = 0;
        foreach (var profile in users.Values)
        {
            totalAge += profile.Age;
            if (profile.Subscribed)
            {
                subscribedUsers++;
            }
        }

        // Calculate average age (rounded down)
        var averageAge = totalAge / totalUsers;
        // Calculate subscribed ratio (to two decimals)
        var subscribedRatio = Math.Round((double)subscribedUsers / totalUsers, 2);

        return new Stats { TotalUsers = totalUsers, AverageAge = averageAge, SubscribedRatio = subscribedRatio };
    }
}

public class Stats
{
    public int TotalUsers { get; set; }
    public int AverageAge { get; set; }
    public double SubscribedRatio { get; set; }
}

class Program
{
    static void Main()
    {
        var um = new UserManager();
        Console.WriteLine(um.addUser("u1", 25, "USA", true));  // true
        Console.WriteLine(um.addUser("u2", 30, "Canada", false));  // true
        Console.WriteLine(um.addUser("u1", 22, "Mexico", true));  // false
        Console.WriteLine(um.getUser("u1"));  // UserProfile with specified attributes
        Console.WriteLine(um.updateUser("u1", 26, null, null));  // true
        Console.WriteLine(um.updateUser("u3", 19, "UK", false));  // false

        Console.WriteLine(string.Join(", ", um.filterUsers(20, 30, "USA", true)));  // ["u1"]
        Console.WriteLine(um.aggregateStats().TotalUsers);  // 2
        Console.WriteLine(um.aggregateStats().AverageAge);  // 27
        Console.WriteLine(um.aggregateStats().SubscribedRatio);  // 0.50
    }
}

This aggregateStats method calculates and returns aggregate statistics about the users in the form of a Stats class object. It first determines TotalUsers, the total number of users. If there are no users, it returns an object with zeroed statistics. Otherwise, it calculates TotalAge by summing the ages of all users and counts SubscribedUsers who are subscribed. It then computes AverageAge by performing integer division of TotalAge by TotalUsers and calculates SubscribedRatio by dividing SubscribedUsers by TotalUsers and rounding to two decimals. The resulting statistics object includes TotalUsers, AverageAge, and SubscribedRatio.