Summary  
This chapter demonstrates how to define and use a generic class with type parameters to implement a LIFO stack supporting any data type via methods like Push, Pop, Peek, Count, and IsEmpty.  

General domain of usage  
Data structures implementation

You can clone the base code from the  <a 
href="https://github.com/Codefinity-Java/GenericClassesTask"
target="_blank"
style="color: #ff8a00; font-weight: 600; text-decoration: none; transition: 0.3s ease-in-out;"
onmouseover="this.style.color='#ff0000'"
onmouseout="this.style.color='#d27204'">GithHub Repository</a>.

A **stack** is a special kind of data structure which stores data according to the **Last In, First Out (LIFO)** principle. A stack has two main methods, namely, `Push` and `Pop`. The `Push` adds a new element to the stack, and `Pop` removes the most recently added element from the stack. You can imagine it like a stack of books, or any other item. By using `Push` you add a new item on the top, and by using `Pop` you remove the item at the top. This is the **LIFO** principle.

The program contains a class which implements the Stack data structure, however, it only supports integers. Make changes in the class code so that it is able to support any data type.

The syntax for creating a generic class is <code>class className<T1, T2, …> { /* class code here */ }</code>.

Hint

```
namespace ConsoleApp
{
    internal class Program
    {
        public class Stack&lt;T&gt;
        {
            private List&lt;T&gt; items;

            public Stack()
            {
                items = new List&lt;T&gt;();
            }

            public void Push(T item)
            {
                items.Add(item);
            }

            public T Pop()
            {
                if (items.Count == 0)
                    throw new InvalidOperationException("Stack is empty");

                T poppedItem = items[items.Count - 1];
                items.RemoveAt(items.Count - 1);
                return poppedItem;
            }

            // Gets the last element, without removing it
            public T Peek()
            {
                if (items.Count == 0)
                {
                    throw new InvalidOperationException("Stack is empty");
                }

                return items[items.Count - 1];
            }

            public int Count
            {
                get { return items.Count; }
            }

            public bool IsEmpty
            {
                get { return items.Count == 0; }
            }
        }

        static void Main(string[] args)
        {
            Stack&lt;string&gt; s1 = new Stack&lt;string&gt;();
            s1.Push("a");
            s1.Push("b");
            s1.Push("c");

            Console.WriteLine(s1.Pop());
            Console.WriteLine(s1.Pop());
            Console.WriteLine(s1.Pop());
        }
    }
}
```

Solution

In this course, we will learn about some advanced C# concepts along with MAUI, which is an application development library. We will learn how to create some interesting GUI applications while keeping them quick and responsive using techniques like Threading. We will make applications that will interact user input and APIs, and apart from that, we will cover some important C# concepts like Reflection and Generics. This course will further improve our programming skills and will give us a strong foundation to move forward towards Web Development.

In this section, we will learn what MAUI is, and how to set up a .NET MAUI application. We will also look at the structure of an MAUI application, and in the end, we will learn how to add some basic elements to our UI. This section will prepare us for the rest of the course where we will be working with more practical concepts.

In this section we will learn about delegates, events and data binding. Using this knowledge we will learn how to make interesting interactive GUI applications.

In this section, we will learn what Threading is and how to use it to keep our applications responsive, and run smoothly while performing resource intensive tasks. We will see how to differs from other similar concepts on C# and what are good practices when implementing Threading in our application. There will also be some interesting tasks to help us in understand this concept on a deeper level.

In this section, we will learn how to make more robust methods, classes and other objects which can work multiple types of input data types, by first learning about Generics and how to implement generic classes, then we will move on to Reflection and how to use reflection for further improving the capabilities of our programs.

Challenge: Implementing a Generic Class