Generic type « generics « Language Basics

For example, the List<T> class in the System.Collections.Generic namespace is defined with one type parameter.

Client code creates an instance of a List<string> or List<int> to specify the type that the list will hold.

 
using System;
public class Stack<T>
{
    private int position;
    T[] data = new T[100];
    public void Push(T obj) { 
        data[position++] = obj; 
    }
    public T Pop() { 
        return data[--position]; 
    }
}

class Test
{
    static void Main()
    {
        Stack<int> stack = new Stack<int>();
        stack.Push(5);
        stack.Push(10);
        int x = stack.Pop();  
        int y = stack.Pop();  
    }
}

A bag is a data structure that can contain zero or more items, including duplicates of items.

 
using System;
using System.Collections.Generic;

public class Bag<T>
{
    private List<T> items = new List<T>();

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

    public T Remove()
    {
        T item = default(T);

        if (items.Count != 0)
        {
            item = items[0];
            items.RemoveAt(0);
        }
        return item;
    }
    // A method to provide an enumerator from the underlying list 
    public IEnumerator<T> GetEnumerator()
    {
        return items.GetEnumerator();
    }

    // A method to remove all items from the bag and return them 
    // as an array 
    public T[] RemoveAll()
    {
        T[] i = items.ToArray();
        items.Clear();
        return i;
    }
}

public class MainClass
{
    public static void Main(string[] args)
    {
        // Create a new bag of strings. 
        Bag<string> bag = new Bag<string>();

        bag.Add("D");
        bag.Add("B");
        bag.Add("G");
        bag.Add("M");
        bag.Add("N");
        bag.Add("I");

        foreach (string elem in bag)
        {
            Console.WriteLine("Element: {0}", elem);
        }

        // Take four strings from the bag and display. 
        Console.WriteLine("Removing individual elements");
        Console.WriteLine("Removing = {0}", bag.Remove());
        Console.WriteLine("Removing = {0}", bag.Remove());

        Console.WriteLine("Bag contents are:");
        foreach (string elem in bag)
        {
            Console.WriteLine("Element: {0}", elem);
        }

        // Remove the remaining items from the bag. 
        Console.WriteLine("Removing all elements");
        string[] s = bag.RemoveAll();

        Console.WriteLine("Bag contents are:");
        foreach (string elem in bag)
        {
            Console.WriteLine("Element: {0}", elem);
        }

    }
}


Element: D
Element: B
Element: G
Element: M
Element: N
Element: I
Removing individual elements
Removing = D
Removing = B
Bag contents are:
Element: G
Element: M
Element: N
Element: I
Removing all elements
Bag contents are: