Various Collection Classes and Their Usage

The following are the various commonly used classes of the System.Collection namespace.

  1. Array List :It represents ordered collection of an object that can be indexed individually.It is basically an alternative to an array. However unlike array you can add and remove items from a list at a specified position using an index and the array resizes itself automatically. It also allows dynamic memory allocation, add, search and sort items in the list.
    using System;
    using System.Collections;
    
    namespace CollectionApplication
    {
        class Program
        {
            static void Main(string[] args)
            {
                ArrayList al = new ArrayList();
    
                Console.WriteLine("Adding some numbers:");
                al.Add(45);
                al.Add(78);
                al.Add(33);
                al.Add(56);
                al.Add(12);
                al.Add(23);
                al.Add(9);
                
                Console.WriteLine("Capacity: {0} ", al.Capacity);
                Console.WriteLine("Count: {0}", al.Count);
                          
                Console.Write("Content: ");
                foreach (int i in al)
                {
                    Console.Write(i + " ");
                }
                Console.WriteLine();
                Console.Write("Sorted Content: ");
                al.Sort();
                foreach (int i in al)
                {
                    Console.Write(i + " ");
                }
                Console.WriteLine();
                Console.ReadKey();
            }
        }
    }
    Adding some numbers:
    Capacity: 8 //Gets or sets the number of elements that the ArrayList can contain.
    Count: 7 //Gets the number of elements actually contained in the ArrayList.
    Content: 45 78 33 56 12 23 9
    Content: 9 12 23 33 45 56 78
  2. Hashtable:It uses a key to access the elements in the collection.A hash table is used when you need to access elements by using key, and you can identify a useful key value. Each item in the hash table has a key/value pair. The key is used to access the items in the collection.
    using System;
    using System.Collections;
    
    namespace CollectionsApplication
    {
       class Program
       {
          static void Main(string[] args)
          {
             Hashtable ht = new Hashtable();
    
    
             ht.Add("001", "Madan Gopal");
             ht.Add("002", "Gopal Rohila");
             ht.Add("003", "Goe Rohile");
             ht.Add("004", "Madan Gopal Rohila");
             ht.Add("005", "M. gopal");
             ht.Add("006", "M. rohila");
             ht.Add("007", "this is gopal");
    
             if (ht.ContainsValue("Madan Gopal"))
             {
                Console.WriteLine("This student name is already in the list");
             }
             else
             {
                ht.Add("008", "aashi");
             }
             // Get a collection of the keys. 
             ICollection key = ht.Keys;
    
             foreach (string k in key)
             {
                Console.WriteLine(k + ": " + ht[k]);
             }
             Console.ReadKey();
          }
       }
    }
    001: Madan Gopal
    002: Gopal Rohila
    003: Goe Rohile
    004: Madan Gopal Rohila
    005: M. gopal
    006: M. rohila
    007: this is gopal
    
  3. SortedList.The SortedList class represents a collection of key-and-value pairs that are sorted by the keys and are accessible by key and by index.A sorted list is a combination of an array and a hash table. It contains a list of items that can be accessed using a key or an index. If you access items using an index, it is an ArrayList, and if you access items using a key, it is a Hashtable. The collection of items is always sorted by the key value.
    class Program
       {
          static void Main(string[] args)
          {
             SortedList sl = new SortedList();
    
             sl.Add("001", "Madan Gopal");
             sl.Add("002", "Gopal Rohila");
             sl.Add("003", "Aashi rohila");
            
    
             if (sl.ContainsValue("Goe"))
             {
                Console.WriteLine("This student name is already in the list");
             }
             else
             {
                sl.Add("004", "Goe");
             }
    
             // get a collection of the keys. 
             ICollection key = sl.Keys;
    
             foreach (string k in key)
             {
                Console.WriteLine(k + ": " + sl[k]);
             }
          }
       }
    001: Madan Gopal
    002: Gopal Rohila
    003: Aashi Rohila
    004: Goe
  4. Stack.It represents a last-in, first out collection of object.It is used when you need a last-in, first-out access of items. When you add an item in the list, it is called pushing the item and when you remove it, it is called popping the item.
    class Program
        {
            static void Main(string[] args)
            {
                Stack st = new Stack();
    
                st.Push('A');
                st.Push('M');
                st.Push('G');
                st.Push('W');
                
                Console.WriteLine("Current stack: ");
                foreach (char c in st)
                {
                    Console.Write(c + " ");
                }
                Console.WriteLine();
                
                st.Push('V');
                st.Push('H');
                Console.WriteLine("The next poppable value in stack: {0}", 
                st.Peek());
                Console.WriteLine("Current stack: ");           
                foreach (char c in st)
                {
                   Console.Write(c + " ");
                }
                Console.WriteLine();
    
                Console.WriteLine("Removing values ");
                st.Pop();
                st.Pop();
                st.Pop();
                
                Console.WriteLine("Current stack: ");
                foreach (char c in st)
                {
                   Console.Write(c + " "); 
                }
            }
        }
    Current stack: 
    W G M A
    The next poppable value in stack: H
    Current stack: 
    H V W G M A
    Removing values
    Current stack: 
    G M A
  5. Queue. It represents a first-in, first out collection of object.It is used when you need a first-in, first-out access of items. When you add an item in the list, it is called enqueue and when you remove an item, it is called deque.
    class Program
       {
          static void Main(string[] args)
          {
             Queue q = new Queue();
    
             q.Enqueue('A');
             q.Enqueue('M');
             q.Enqueue('G');
             q.Enqueue('W');
             
             Console.WriteLine("Current queue: ");
             foreach (char c in q)
                Console.Write(c + " ");
             Console.WriteLine();
             q.Enqueue('V');
             q.Enqueue('H');
             Console.WriteLine("Current queue: ");         
             foreach (char c in q)
                Console.Write(c + " ");
             Console.WriteLine();
             Console.WriteLine("Removing some values ");
             char ch = (char)q.Dequeue();
             Console.WriteLine("The removed value: {0}", ch);
             ch = (char)q.Dequeue();
             Console.WriteLine("The removed value: {0}", ch);
             Console.ReadKey();
          }
       }
    Current queue: 
    A M G W 
    Current queue: 
    A M G W V H 
    Removing values
    The removed value: A
    The removed value: M
  6. BitArray. It represents an array of the binary representation using the values 1 and 0. It is used when you need to store the bits but do not know the number of bits in advance. You can access items from the BitArray collection by using an integer index, which starts from zero.
    static void Main(string[] args)
            {
                //creating two  bit arrays of size 8
                BitArray ba1 = new BitArray(8);
                BitArray ba2 = new BitArray(8);
                byte[] a = { 60 };
                byte[] b = { 13 };
                
                //storing the values 60, and 13 into the bit arrays
                ba1 = new BitArray(a);
                ba2 = new BitArray(b);
    
                //content of ba1
                Console.WriteLine("Bit array ba1: 60");
                for (int i = 0; i < ba1.Count; i++)
                {
                    Console.Write("{0, -6} ", ba1[i]);
                }
                Console.WriteLine();
                
                //content of ba2
                Console.WriteLine("Bit array ba2: 13");
                for (int i = 0; i < ba2.Count; i++)
                {
                    Console.Write("{0, -6} ", ba2[i]);
                }
                Console.WriteLine();
               
                
                BitArray ba3 = new BitArray(8);
                ba3 = ba1.And(ba2);
    
                //content of ba3
                Console.WriteLine("Bit array ba3 after AND operation: 12");
                for (int i = 0; i < ba3.Count; i++)
                {
                    Console.Write("{0, -6} ", ba3[i]);
                }
                Console.WriteLine();
    
                ba3 = ba1.Or(ba2);
                //content of ba3
                Console.WriteLine("Bit array ba3 after OR operation: 61");
                for (int i = 0; i < ba3.Count; i++)
                {
                    Console.Write("{0, -6} ", ba3[i]);
                }
                Console.WriteLine();
                
                Console.ReadKey();
            }
    Bit array ba1: 60 
    False False True True True True False False 
    Bit array ba2: 13
    True False True True False False False False 
    Bit array ba3 after AND operation: 12
    False False True True False False False False 
    Bit array ba3 after OR operation: 61
    True False True True False False False False
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2 thoughts on “Collections in C#

  1. Nice Explaination, Now i have cleared all my doubts by reading this blog, Keep it up. It would be very beneficial for readers.

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