C# Labs - Generics, LINQ & JSON

Lab 16: Generics & Constraints

Expert

Coding Challenge

Your Task: Create a generic class and a generic method with constraints, then use them with different type arguments.

Detailed Requirements:
1. Create a generic class Box<T> with a read-only property and method:

class Box<T>
{
    public T Value { get; private set; }
    public Box(T value) { Value = value; }
    public void SetValue(T value) { Value = value; }
    public void Describe() => Console.WriteLine($"T is {typeof(T).Name}");
}

2. Create a generic method with a constraint:

static class Utils
{
    public static T Max<T>(T a, T b) where T : IComparable<T>
    {
        return a.CompareTo(b) >= 0 ? a : b;
    }
}

3. Use your types: Instantiate Box<int> and Box<string>, print their values, call Describe(), and use Utils.Max for ints and strings.

💡 Pro Tips:
• Prefer generics over object casting for type safety and performance
• Use constraints (where) to express capabilities required (class, struct, interfaces, parameterless ctor)
• Avoid boxing/unboxing by using value-type generics directly
• Generic methods can live in non-generic classes, too

Expected Output:

Box<int> value: 42
Box<string> value: hello
T is Int32
Max int: 10
Max string: orange

Requirements Checklist

Define generic class Box<T> with a property

Implement generic method Max<T> with IComparable constraint

Instantiate Box<int> and Box<string>

Print Box values and call Describe()

Use Utils.Max for ints and strings

Code compiles and prints expected lines

using System;

class Box<T>
{
    public T Value { get; private set; }
    public Box(T value) { Value = value; }
    public void SetValue(T value) { Value = value; }
    public void Describe() => Console.WriteLine($"T is {typeof(T).Name}");
}

static class Utils
{
    public static T Max<T>(T a, T b) where T : IComparable<T>
    {
        return a.CompareTo(b) >= 0 ? a : b;
    }
}

class GenericsDemo
{
    static void Main()
    {
        // TODO: Instantiate generic classes and use generic method
        // var intBox = new Box<int>(42);
        // var strBox = new Box<string>("hello");
        // Console.WriteLine($"Box<int> value: {intBox.Value}");
        // Console.WriteLine($"Box<string> value: {strBox.Value}");
        // intBox.Describe();
        // Console.WriteLine($"Max int: {Utils.Max(10, 3)}");
        // Console.WriteLine($"Max string: {Utils.Max("apple", "orange")}");
        
        
    }
}

Output

// Click "Run Code" to compile and execute

Hints & Tips

• Generic class: class Box<T> { T Value { get; } }

• Constraint: where T : IComparable<T>

• Instantiate: new Box<int>(42), new Box<string>("hi")

• typeof(T).Name shows the type argument at runtime

Progress: 0/6

Score: 0/100

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Lab 17: LINQ Advanced (GroupBy & Join)

Expert

Coding Challenge

Your Task: Use LINQ to group items and join related collections to produce aggregated, ordered results.

Detailed Requirements:
1. Create data models and lists:

class Student { public int Id; public string Name; public int DeptId; }
class Department { public int Id; public string Name; }

Make List<Student> and List<Department> with sample data.

2. Group students by department (GroupBy): Produce counts per department.
3. Join/group-join with departments: Show department names with counts and order by count descending.
4. Join students to departments: Show each student's name and department using Join, ordered by student name.
5. Use projections: Select into anonymous types.
6. Materialize results: Use ToList() or ToDictionary() where appropriate.

💡 Pro Tips:
• Remember using System.Linq;
• GroupJoin can compute aggregates from related items
• LINQ is deferred until enumerated; call ToList() to execute immediately

Expected Output:

Students per department:
Engineering: 3
Marketing: 2

Join sample:
Alice -> Engineering
Bob -> Engineering
Chloe -> Marketing
David -> Engineering
Eve -> Marketing

Requirements Checklist

Create List<Student> and List<Department>

Use GroupBy for counts per department

Use Join or GroupJoin with Department

Order results by count or name

Project with Select into anonymous types

Materialize with ToList/ToDictionary

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

class Student { public int Id; public string Name; public int DeptId; }
class Department { public int Id; public string Name; }

class LinqAdvanced
{
    static void Main()
    {
        // TODO: Build sample data
        // var depts = new List<Department> {
        //     new Department{ Id = 1, Name = "Engineering" },
        //     new Department{ Id = 2, Name = "Marketing" }
        // };
        // var students = new List<Student> {
        //     new Student{ Id=1, Name="Alice", DeptId=1 },
        //     new Student{ Id=2, Name="Bob", DeptId=1 },
        //     new Student{ Id=3, Name="Chloe", DeptId=2 },
        //     new Student{ Id=4, Name="David", DeptId=1 },
        //     new Student{ Id=5, Name="Eve", DeptId=2 }
        // };
        
        
        // TODO: GroupBy + Join for counts per department
        // var grouped = students
        //     .GroupBy(s => s.DeptId)
        //     .Join(depts, g => g.Key, d => d.Id, (g, d) => new { Dept = d.Name, Count = g.Count() })
        //     .OrderByDescending(x => x.Count)
        //     .ToList();
        // Console.WriteLine("Students per department:");
        // foreach (var x in grouped) Console.WriteLine($"{x.Dept}: {x.Count}");
        
        
        // TODO: Join students to departments and order by name
        // var joined = students.Join(depts, s => s.DeptId, d => d.Id, (s, d) => new { s.Name, Dept = d.Name })
        //                      .OrderBy(x => x.Name)
        //                      .ToList();
        // Console.WriteLine("\nJoin sample:");
        // foreach (var item in joined) Console.WriteLine($"{item.Name} -> {item.Dept}");
        
        
    }
}

Output

// Click "Run Code" to compile and execute

Hints & Tips

• Remember using System.Linq;

• Group + join: students.GroupBy(s => s.DeptId).Join(depts, g => g.Key, d => d.Id, ...)

• Materialize: .ToList() to execute queries

• Query syntax also works: from s in students join d in depts on s.DeptId equals d.Id select ...

Progress: 0/6

Score: 0/100

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Lab Results

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Lab 18: JSON with System.Text.Json

Expert

Coding Challenge

Your Task: Serialize and deserialize objects using System.Text.Json with options.

Detailed Requirements:
1. Create a POCO:

class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
    public string Email { get; set; }
}

2. Serialize with options: Use JsonSerializerOptions { WriteIndented = true }.
3. Deserialize back to object: From the JSON string to Person.
4. Print both: Pretty JSON, then the deserialized object's properties.
5. Optional: Add [JsonPropertyName("...")] annotations (requires System.Text.Json.Serialization).

💡 Pro Tips:
• Avoid trailing commas in JSON
• Options like PropertyNameCaseInsensitive help with casing mismatches
• Prefer System.Text.Json in modern .NET for performance

Expected Output:

Serialized JSON:
{
  "Name": "Alice",
  "Age": 25,
  "Email": "alice@example.com"
}

Deserialized: Alice (25) - alice@example.com

Requirements Checklist

Define Person class with Name, Age, Email

Serialize with JsonSerializer and WriteIndented

Deserialize JSON back to Person

Print serialized JSON and deserialized fields

Use System.Text.Json namespaces

Code compiles and runs

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
    public string Email { get; set; }
}

class JsonDemo
{
    static void Main()
    {
        // TODO: Serialize and deserialize with System.Text.Json
        // var person = new Person { Name = "Alice", Age = 25, Email = "alice@example.com" };
        // var options = new JsonSerializerOptions { WriteIndented = true };
        // string json = JsonSerializer.Serialize(person, options);
        // Console.WriteLine("Serialized JSON:");
        // Console.WriteLine(json);
        // var p2 = JsonSerializer.Deserialize<Person>(json);
        // Console.WriteLine($"\nDeserialized: {p2.Name} ({p2.Age}) - {p2.Email}");
        
        
    }
}

Output

// Click "Run Code" to compile and execute

Hints & Tips

• Namespaces: using System.Text.Json; (+ ...Serialization if using attributes)

• Options: new JsonSerializerOptions { WriteIndented = true }

• Serialize: JsonSerializer.Serialize(obj, options)

• Deserialize: JsonSerializer.Deserialize<Type>(json)

Progress: 0/6

Score: 0/100

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C# Programming Labs

Generics, LINQ Advanced & JSON - Module 6

Requirements Checklist

Lab Results

Requirements Checklist

Lab Results

Requirements Checklist

Lab Results