Multiple generic parameters in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of generic class with two type parameters

What is the output of the following C# program?

C Sharp (C#)

using System;

class Pair<T, U>
{
    public T First { get; set; }
    public U Second { get; set; }

    public Pair(T first, U second)
    {
        First = first;
        Second = second;
    }

    public void Print()
    {
        Console.WriteLine($"{First} and {Second}");
    }
}

class Program
{
    static void Main()
    {
        var pair = new Pair<int, string>(5, "hello");
        pair.Print();
    }
}

A 5 and hello

B hello and 5

C 5hello

D Compilation error

💡 Hint

Look at how the generic parameters are used and printed in the Print method.

The Pair class has two generic parameters T and U. The Print method prints First and Second separated by ' and '. Since First is 5 and Second is "hello", the output is "5 and hello".

❓ Predict Output

intermediate

Output of generic method with two parameters

What is the output of this C# program?

C Sharp (C#)

using System;

class Utils
{
    public static void Swap<T, U>(ref T a, ref U b)
    {
        Console.WriteLine($"Swapping {a} and {b}");
    }
}

class Program
{
    static void Main()
    {
        int x = 10;
        string y = "test";
        Utils.Swap(ref x, ref y);
    }
}

A Swapping 10 and test

B Swapping test and 10

C Compilation error due to different types

D Runtime error

💡 Hint

Generic methods can have multiple type parameters and can accept different types.

The Swap method prints the values of a and b. Since a is 10 and b is "test", it prints "Swapping 10 and test".

🔧 Debug

advanced

Identify the error in generic class instantiation

What error does the following code produce?

C Sharp (C#)

class Container<T, U>
{
    public T Item1;
    public U Item2;
}

class Program
{
    static void Main()
    {
        Container<int> c = new Container<int, string>();
    }
}

A CS0029: Cannot implicitly convert type 'Container<int, string>' to 'Container<int>'

B CS0311: The type arguments for method cannot be inferred

C No error, compiles successfully

D CS0305: Using the generic type 'Container<T, U>' requires 2 type arguments

💡 Hint

Check how many generic parameters the class Container expects.

The class Container requires two type parameters but only one is provided in the declaration, causing CS0305 error.

📝 Syntax

advanced

Which option correctly declares a generic class with two parameters?

Select the correct syntax to declare a generic class with two type parameters T and U.

A class MyClass<T U> { }

B class MyClass<T; U> { }

C class MyClass<T, U> { }

D class MyClass<T> U { }

💡 Hint

Generic parameters are separated by commas inside angle brackets.

The correct syntax uses commas to separate generic parameters inside angle brackets: .

🚀 Application

expert

Determine the number of items in a generic dictionary

Given the following code, how many items are in the dictionary after execution?

C Sharp (C#)

using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<int, string> dict = new Dictionary<int, string>();
        dict.Add(1, "one");
        dict.Add(2, "two");
        dict[3] = "three";
        dict[2] = "deux";
    }
}

A 4

B 3

C 2

D Compilation error

💡 Hint

Adding a key that already exists updates its value, not adds a new item.

The dictionary has keys 1, 2, and 3. The value for key 2 is updated, so total items remain 3.