Sorted List - Generic

C# Sorted List

In c#, SortedList is a generic type of collection and it is used to store a collection of key/value pairs that are sorted by key based on the associated IComparer<T> implementation.

By default, the sortedlist will sort a key/value pairs in ascending order of the key and the sortedlist will allow storing only the strongly-typed objects i.e. the key/value pairs of the specified data type.

In c#, the sortedlist will allow us to store duplicate values but the keys must be unique and cannot be null to identify the values in sortedlist and the size of sortedlist will vary dynamically so you can add or remove elements from the sortedlist based on our application requirements.

C# includes two type of SortedList, generic SortedList and non-generic SortedList. Generic SortedList denotes with angel bracket: SortedList<TKey,TValue> where TKey is for type of key and TValue is for type of value. Non-generic type do not specify the type of key and values.

You can instantiate SortedList<TKey, TValue> by specifying type for key and value, as shown below.

Ex. SortedList<TKey, TValue> slist = new SortedList<TKey, TValue>();

Properties

Property	Description
Capacity	Gets or sets the number of elements that the SortedList<TKey,TValue> can store
Count	Gets the total number of elements exists in the SortedList<TKey,TValue>.
IsReadOnly	Returns a boolean indicating whether the SortedList<TKey,TValue> is read-only.
Item	Gets or sets the element with the specified key in the SortedList<TKey,TValue>.
Keys	Get list of keys of SortedList<TKey,TValue>
Values	Get list of values in SortedList<TKey,TValue>.

Method

Method	Description
Add	Add key-value pairs into SortedList<TKey, TValue>.
Remove	Removes element with the specified key.
Remove At	Removes element at the specified index.
Contains Key	Checks whether the specified key exists in SortedList<TKey, TValue>.
Contains Value	Checks whether the specified key exists in SortedList<TKey, TValue>.
Clear	Removes all the elements from SortedList<TKey, TValue>.
Index Of Key	Returns an index of specified key stored in internal array of SortedList<TKey, TValue>
Index Of Value	Returns an index of specified value stored in internal array of SortedList<TKey,   TValue>
Try Get Value	Returns true and assigns the value with specified key, if key does not exists then return false.

Example

 class CollectionExamples

    {

        public static void Main(String[] args)

        {

            SortedList<int, string> sl = new SortedList<int, string>();

            sl.Add(3, "Three");

            sl.Add(1, "One");

            sl.Add(2, "Two");

            sl.Add(4, null);

            foreach (var item in sl.Keys)

            {

                Console.WriteLine("Sorted List {0}", item);

            }

            Console.ReadLine();

        }

    }

Dictionary

C# Dictionary

• The Dictionary<TKey, TValue> class is a generic collection class in the System.Collection.Generics namespace. TKey denotes the type of key and TValue is the type of TValue.
• There is a non-generic collection called a Hashtable, which does the same thing, except that it operates on type object. However, you want to avoid the non-generic collections and use their generic counterparts instead
• Dictionary cannot include duplicate or null keys, where as values can be duplicated or set as null. Keys must be unique otherwise it will throw a runtime exception.
• The capacity of a Dictionary is the number of elements that Dictionary can hold.

Properties

Property	Description
Count	Gets the total number of elements exists in the Dictionary<TKey,TValue>              .
IsReadOnly	Returns a boolean indicating whether the Dictionary<TKey,TValue> is read-only.
Item	Gets or sets the element with the specified key in the Dictionary<TKey,TValue>.
Keys	Returns collection of keys of Dictionary<TKey,TValue>.
Values	Returns collection of values in Dictionary<TKey,TValue>.

Methods

Method	Description
Add	Add key-value pairs in Dictionary<TKey, TValue> collection.
Remove	Removes the first occurrence of specified item from the Dictionary<TKey, TValue>.
ContainsKey	Checks whether the specified key exists in Dictionary<TKey, TValue>.
ContainsValue	Checks whether the specified key exists in Dictionary<TKey, TValue>.
Clear	Removes all the elements from Dictionary<TKey, TValue>.
TryGetValue	Returns true and assigns the value with specified key, if key does not exists then return false.

Example

 public static void Main(String[] args)

   {

           

            Dictionary<int, string> _dictionary =  new Dictionary<int, string>();

            // Adding key/value pairs  

            _dictionary.Add(1, "Hello");

            _dictionary.Add(2, "This is");

            _dictionary.Add(3, "Blog for C#");

            _dictionary.Remove(1); //Remove value which key is 1

            Console.WriteLine("Is Key Exist?: {0}",_dictionary.ContainsKey(2));//Return True

            Console.WriteLine("Is Value Exist?: {0}", _dictionary.ContainsValue("This is"));//Return True

            foreach (KeyValuePair<int, string> ele1 in _dictionary)

            {

                Console.WriteLine("{0} and {1}",

                          ele1.Key, ele1.Value);

            }

            Console.ReadLine();

           

    }

List

 What is C# List<T>

• List<T> class represents the list of objects which can be accessed by index. It comes under the System.Collection.Generic namespace. 
• List class can be used to create a collection of different types like integers, strings etc. List<T> class also provides the methods to search, sort, and manipulate lists.
• It is different from the arrays. A List<T> can be resized dynamically but arrays cannot.
• List<T> class can accept null as a valid value for reference types and it also allows duplicate elements.
• If the Count becomes equals to Capacity, then the capacity of the List increased automatically by reallocating the internal array. The existing elements will be copied to the new array before the addition of the new element.
• List<T> class is the generic equivalent of ArrayList class by implementing the IList<T> generic interface.
• This class can use both equality and ordering comparer.
• List<T> class is not sorted by default and elements are accessed by zero-based index.
• For very large List<T> objects, you can increase the maximum capacity to 2 billion elements on a 64-bit system by setting the enabled attribute of the configuration element to true in the run-time environment.

Properties

Properties	Description
Capacity	Gets or sets the total number of elements the internal data structure can hold without resizing.
Count	Returns the total number of elements exists in the List<T>
Item	Gets or sets the element at the specified index.

Methods

Method	Usage
Add	Adds an element at the end of a List<T>.
AddRange	Adds elements of the specified collection at the end of a List<T>.
BinarySearch	Search the element and returns an index of the element.
Clear	Removes all the elements from a List<T>.
Contains	Checks whether the speciied element exists or not in a List<T>
Find	Finds the first element based on the specified predicate function.
ForEach	Iterates through a List<T>.
Remove<T>	Removes the first occurrence of a specific object from the List<T>.
Remove All<T>	Removes all the elements that match the conditions defined by the specified predicate.
Remove At(Int32)	Removes the element at the specified index of the List<T>.
RemoveRange(Int32,Int32)	Removes a range of elements from the List<T>.
Reverse()	Reverses the order of the elements in the List<T> or a portion of it.
Sort()	Sorts the elements or a portion of the elements in the List<T> using either the specified or default IComparer<T> implementation or a provided Comparison<T> delegate to compare list elements.
ToArray()	Copies the elements of the List<T> to a new array.

Example:

class CollectionExamples

    {

        public static void Main(String[] args)

        {

            // Creating an List<T> of Integers 

            List<int> _List = new List<int>();

            // Adding elements to List 

            _List.Add(1);

            _List.Add(3);

            _List.Add(4);

            _List.Add(7);

            _List.Add(9);

            _List.Add(18);

            _List.Add(22);

            Console.WriteLine("Elements Present in List:\n");

            int p = 0;

            // Displaying the elements of List 

            foreach (int k in _List)

            {

                Console.Write("At Position {0}: ", p);

                Console.WriteLine(k);

                p++;

            }

            Console.WriteLine(" ");

            // removing the element at index 3 

            Console.WriteLine("Removing the element at index 3\n");

            _List.RemoveAt(4);

            int p1 = 0;

            // Displaying the elements of List 

            foreach (int n in _List)

            {

                Console.Write("At Position {0}: ", p1);

                Console.WriteLine(n);

                p1++;

            }

        }

Queue(Non Generic)

Queue:

C# includes a Queue collection class in the System.Collection namespace. Queue stores the elements in FIFO style (First In First Out), exactly opposite of the Stack collection. It contains the elements in the order they were added.

Queue collection allows multiple null and duplicate values.

Use the Enqueue() method to add elements into Queue

The Dequeue() method returns and removes elements from the beginning of the Queue. Calling the Dequeue() method on an empty queue will throw an exception.

The Peek() method always returns top most element.

Properties of queue

Count - Returns the total count of elements in the Queue.

Methods of queue

1. Enqueue: Adds an item into the queue.
2. Dequeue: Removes and returns an item from the beginning of the queue.
3. Peek: Returns an first item from the queue
4. Contains: Checks whether an item is in the queue or not
5. Clear: Removes all the items from the queue.
6. TrimToSize: Sets the capacity of the queue to the actual number of items in the queue.

1.Enqueue: Enqueue method is used to add element in queue.you can add element of any datatype as it's a non-generic collection.

Example

 class CollectionExamples

    {

        static void Main(string[] args)

        {

            Queue _queue = new Queue();

            _queue.Enqueue(1);

            _queue.Enqueue(2);

            _queue.Enqueue(3);

            _queue.Enqueue(3); //it allows duplicate

            _queue.Enqueue(null); // it allows null

            foreach(var item in _queue)

            {

                Console.WriteLine(item);

            }

            

            Console.ReadLine();

        }

    }

2.Dequeue: 

Dequeue() method is used to retrieve the top most element in a queue collection.

Dequeue() removes and returns a first element from a queue because the queue stores elements in FIFO order.

 

Calling Dequeue() method on empty queue will throw InvalidOperation exception. So always check that the total count of a queue is greater than zero before calling the Dequeue() method on a queue.

Example

 class CollectionExamples

    {

        static void Main(string[] args)

        {

            Queue _queue = new Queue();

            _queue.Enqueue(1);

            _queue.Enqueue(2);

            _queue.Enqueue(3);

            _queue.Enqueue(3); //it allows duplicate

            _queue.Enqueue(null); // it allows null

           Console.WriteLine("Length Before Dequeue {0}", _queue.Count);

           Console.WriteLine("Calling Dequeue {0}", _queue.Dequeue()); //Return first element and remove it.

           Console.WriteLine("Length After Dequeue {0}", _queue.Count);

            Console.ReadLine();

        }

    }

Output:

Length Before Dequeue 5

Calling Dequeue 1

Length After Dequeue 4

3. Peek() : The Peek() method always returns the first item from a queue collection without removing it from the queue. 

Calling Peek() and Dequeue() methods on an empty queue collection will throw a run time exception "InvalidOperationException".

Example

 class CollectionExamples

    {

        static void Main(string[] args)

        {

            Queue _queue = new Queue();

            _queue.Enqueue(1);

            _queue.Enqueue(2);

            _queue.Enqueue(3);

            _queue.Enqueue(3); //it allows duplicate

            _queue.Enqueue(null); // it allows null

           Console.WriteLine("Length Before Dequeue {0}", _queue.Count);

           Console.WriteLine("Calling Dequeue {0}", _queue.Peek()); //Return first element

           Console.WriteLine("Length After Dequeue {0}", _queue.Count);

            Console.ReadLine();

        }

    }

Output

Length Before Dequeue 5

Calling Dequeue 1

Length After Dequeue 5

4.Contains()
The Contains() method checks whether an item exists in a queue. It returns true if the specified item exists; otherwise it returns false.

Example

 class CollectionExamples

    {

        static void Main(string[] args)

        {

            Queue _queue = new Queue();

            _queue.Enqueue(1);

            _queue.Enqueue(2);

            _queue.Enqueue(3);

            _queue.Enqueue(3); //it allows duplicate

            _queue.Enqueue(null); // it allows null

           Console.WriteLine(_queue.Contains(1)); // it will return true

        

            Console.ReadLine();

        }

    }

5.Clear() :The Clear() method removes all the items from a queue.

Example

 static void Main(string[] args)

        {

            Queue _queue = new Queue();

            _queue.Enqueue(1);

            _queue.Enqueue(2);

            _queue.Enqueue(3);

            _queue.Enqueue(3); //it allows duplicate

            _queue.Enqueue(null); // it allows null

            _queue.Clear();

           Console.WriteLine(_queue.Count);//it will return 0

        

            Console.ReadLine();

        }

Stack(Non generic)

C# Stack

C# includes a special type of collection which stores elements in LIFO style (Last In First Out).

Stack allows null value and also duplicate values. It provides a Push() method to add a value and Pop() or Peek() methods to retrieve values.

Use the Push() method to add elements into Stack.

The Pop() method returns and removes elements from the top of the Stack. Calling the Pop() method on the empty Stack will throw an exception.

The Peek() method always returns top most element in the Stack.

Properties

Count- Return the total count of element in the stack.

Method

1. Push: Inserts an item at the top of the stack.
2. Peek: Returns the top item from the stack.
3. Pop: Removes and returns items from the top of the stack.
4. Contains: Checks whether an item exists in the stack or not.
5. Clear: Removes all items from the stack.

1. Push: The Push() method adds values into the Stack. It allows value of any datatype

Example:

  static void Main(string[] args)

        {

            Stack _stack = new Stack();

            _stack.Push(1);

            _stack.Push(2);

            _stack.Push(3);

            foreach (var item in _stack)

            Console.WriteLine(item);

            Console.ReadLine();

        }

2.Peek: The Peek() method returns the last (top-most) value from the stack. Calling Peek() method on empty stack will throw InvalidOperationException. So always check for elements in the stack before retrieving elements using the Peek() method.

The below program return 4 as an output.

Example

class CollectionExamples

    {

        static void Main(string[] args)

        {

            Stack _stack = new Stack();

            _stack.Push(1);

            _stack.Push(2);

            _stack.Push(3);

            _stack.Push(4);

            Console.WriteLine(_stack.Peek());

            Console.ReadLine();

        }

    }

3.Pop(): You can also retrieve the value using the Pop() method. The Pop() method removes and returns the value that was added last to the Stack. The Pop() method call on an empty stack will raise an InvalidOperationException. So always check for number of elements in stack must be greater than 0 before calling Pop() method.

Below program retrurn 3,2 and  1 as an output.

Example

 class CollectionExamples

    {

        static void Main(string[] args)

        {

            Stack _stack = new Stack();

            _stack.Push(1);

            _stack.Push(2);

            _stack.Push(3);

            _stack.Push(4);

            _stack.Pop();

            foreach (var item in _stack)

                Console.WriteLine("items {0}", item);

            Console.ReadLine();

        }

    }

    

4.Contains():The Contains() method checks whether the specified item exists in a Stack collection or not. It returns true if it exists; otherwise it returns false.

Below program return true as an output.

class CollectionExamples

    {

        static void Main(string[] args)

        {

            Stack _stack = new Stack();

            _stack.Push(1);

            _stack.Push(2);

            _stack.Push(3);

            _stack.Push(4);

            Console.WriteLine("Is Exist : {0}", _stack.Contains(1));

            Console.ReadLine();

        }

    }

5.Clear() :The Clear() method removes all the values from the stack.

class CollectionExamples

    {

        static void Main(string[] args)

        {

            Stack _stack = new Stack();

            _stack.Push(1);

            _stack.Push(2);

            _stack.Push(3);

            _stack.Push(4);

           _stack.clear();

            Console.WriteLine("Total {0}",_stack.count);

            Console.ReadLine();

        }

Sorted List(Non generic)

C# Sorted List(Non generic)

In C#, SortedList is a collection of key/value pairs which are sorted according to keys. By default, this collection sort the key/value pairs in ascending order.

Non-generic SortedList is defined under System.Collections namespace

Properties of Sorted List

1. Capacity: Gets or sets the number of elements that the SortedList instance can store.
2. Count: Gets the number of elements actually contained in the SortedList.
3. IsFixedSize: Gets a value indicating whether the SortedList has a fixed size.
4. IsReadOnly: Gets a value indicating whether the SortedList is read-only.
5. Item : Gets or sets the element at the specified key in the SortedList.
6. Keys: Get list of keys of SortedList.
7. Values: Get list of values in SortedList.

Method of Sorted List

1) Add(object key, object value): Add key-value pairs into SortedList.

Key cannot be null but value can be null. Also, datatype of all keys must be same, so that it can compare otherwise it will throw runtime exception.

Non-generic SortedList collection can contain key and value of any data type. So values must be cast to the appropriate data type otherwise it will give compile-time error.

Example:

class CollectionExamples

    {

        static void Main(string[] args)

        {

            SortedList sl = new SortedList();

            sl.Add(3, "Three");

            sl.Add(1, "One");

            sl.Add(2, "Two");

            sl.Add(4, null);

            foreach (var item in sl.Keys)

            {

                Console.WriteLine("Sorted List {0}", item);

            }

            Console.ReadLine();

        }

    }

Output:

Sorted List 1

Sorted List 2

Sorted List 3

Sorted List 4

2) Remove(object key): Removes element with the specified key.

3) RemoveAt(int index): Removes element at the specified index.

Example

 static void Main(string[] args)

        {

            SortedList sl = new SortedList();

            sl.Add(3, "Three");

            sl.Add(1, "One");

            sl.Add(2, "Two");

            sl.Add(4, null);

            sl.Remove(3);//Remove element whose key is two

            sl.RemoveAt(0);//Remove element whose index is 1

            foreach (DictionaryEntry de in sl)

            {

                Console.WriteLine("Sorted List {0}", de.Key);

            }

            Console.ReadLine();

        }

Output:

Sorted List 2

Sorted List 4

4)Contains: This method is used to check whether a SortedList object contains a specific key.

5)ContainsKey: This method is used to check whether a SortedList object contains a specific key.

6)ContainsValue: This method is used to check whether a SortedList object contains a specific value.

Example:

        static void Main(string[] args)

        {

            SortedList sl = new SortedList();

            sl.Add(3, "Three");

            sl.Add(1, "One");

            sl.Add(2, "Two");

            sl.Add(4, null);

            Console.WriteLine("Contains {0}",sl.Contains(3)); // Return true if given key is found.

            Console.WriteLine("Contains Key {0}", sl.ContainsKey(3));// Return true if given key is found.

            Console.WriteLine("Contains value {0}", sl.ContainsValue("Three"));//Return true if given value found.

            

            Console.ReadLine();

        }

GetByIndex(int index) : Returns the value by index stored in internal array

GetKey(int index): Returns the key stored at specified index in internal array

IndexOfKey(object key): Returns an index of specified key stored in internal array

IndexOfValue(object value) : Returns an index of specified value stored in internal array

Note:Internally, SortedList maintains two object[] array, one for keys and another for values. So when you add key-value pair, it runs a binary search using the key to find an appropriate index to store a key and value in respective arrays. It re-arranges the elements when you remove the elements from it.

HashTable in C#

What is HashTable?

C# includes Hashtable collection in System.Collections namespace, which is similar to generic collection. The Hashtable collection stores key-value pairs. It optimizes lockups by computing the hash code of each key and stores it in a different bucket internally and then matches the hash code of the specified key at the time of accessing values.

Properties of Hashtable

Count: Gets the total count of key/value pairs in the Hashtable.

IsReadOnly: Gets boolean value indicating whether the Hashtable is read-only.

Item :Gets or sets the value associated with the specified key.

Keys :Gets an ICollection of keys in the Hashtable.

Values : Gets an ICollection of values in the Hashtable

Methods of HashTable

Add : The Add() method adds an item with a key and value into the Hashtable. Key and value can be of any data type. Key cannot be null whereas value can be null.

Example

static void Main(string[] args)

         {

            Hashtable ht = new Hashtable();

            ht.Add(1, "One");

            ht.Add(2, 2);

            ht.Add(3, 3.0);

            ht.Add(4, null);

        }

Remove: Removes the item with the specified key from the hashtable.

Example

static void Main(string[] args)

         {

            Hashtable ht = new Hashtable();

            ht.Add(1, "One");

            ht.Add(2, 2);

            ht.Add(3, 3.0);

            ht.Add(4, null);

            ht.Remove(1);

        }

Clear: Removes all the items from the hashtable.

Example

 static void Main(string[] args)

         {

            Hashtable ht = new Hashtable();

            ht.Add(1, "One");

            ht.Add(2, 2);

            ht.Add(3, 3.0);

            ht.Add(4, null);

            ht.Clear();

        }

Contains: Checks whether the hashtable contains a specific key.

Example

 static void Main(string[] args)

         {

            Hashtable ht = new Hashtable();

            ht.Add(1, "One");

            ht.Add(2, 2);

            ht.Add(3, 3.0);

            ht.Add(4, null);

            ht.Contains(1);//return true;

            ht.Contains(1);//return true;

            ht.Contains(5); //return false

        }

ContainsKey: Checks whether the hashtable contains a specific key it work similar as Contains.

ContainsValue: Checks whether the hashtable contains a specific value.

 static void Main(string[] args)

         {

            Hashtable ht = new Hashtable();

            ht.Add(1, "One");

            ht.Add(2, 2);

            ht.Add(3, 3.0);

            ht.Add(4, null);

            ht.ContainsValue(5); //return true

        }

GetHash: Returns the hash code for the specified key.

Summary:

• Hashtable stores key-value pairs of any datatype where the Key must be unique.
• The Hashtable key cannot be null whereas the value can be null.
• Hashtable retrieves an item by comparing the hashcode of keys. So it is slower in performance than Dictionary collection.
• Hashtable uses the default hashcode provider which is object.GetHashCode(). You can also use a custom hashcode provider.
• Use DictionaryEntry with foreach statement to iterate Hashtable.