Access Specifiers in C#

Access Specifiers defines the scope of a class member (variable or function).

Five types of access specifiers:

• Public Access Specifiers - can be accessed from anywhere even outside the namespace
• Private Access Specifiers - hides its member variable and method from other class and methods. However, get(return value- retrieving value from private field)  set(return void - store value in private variables) property can retrieve or store private access modifiers values.
• Protected Access Specifiers - member variable and method can only be accessed in child class
• Internal Access Specifiers - hides its member variables and methods from other classes and objects in other namespace
• Protected Internal Access Specifiers.- allows its members to be accessed in derived class, containing class or classes within the same namespace.

Dictionary in C#

Category	Features	Name Space	Inherits from
IDictionary	1.      IDictionary implementations fall into three categories: read-only, fixed-size, variable-size.	System.Collections	ICollection
IDictionary<TKey, TValue>	1.      The IDictionary<TKey, TValue> interface is the base interface for generic collections of key/value pairs. 2.      IDictionary is a "more generic" type .	System.Collections.Generic	ICollection<KeyValuePair<TKey, TValue>
Dictionary	This implementation does not provide a synchronized (thread-safe) wrapper for a DictionaryBase, but derived classes can create their own synchronized versions. Solution: Lock collection to avoid changes made by other threads	System.Collections	IDictionary
Dictionary<TKey, TValue>	1.      Provides a mapping from a set of keys to a set of values. 2.      Retrieving a value by using its key is very fast because class is implemented as a hash table. 3.      A Dictionary<TKey, TValue> can support multiple readers concurrently, as long as the collection is not modified.	System.Collections.Generic	IDictionary<TKey, TValue>

IEnumerable, ICollection, IList and List an Overview

Category	Methods	Name Space	Inherits from	Use
IEnumerable	GetEnumerator	System.Collections		Provided read-only access to elements in that collection via iteration.
IEnumerable<T> (Type safe version)	GetEnumerator	System.Collections.Generic	IEnumerable
ICollection	1.      Defines size, enumerators 2.      Asynchronization methods for all nongeneric collections.	System.Collections.ICollection	IEnumerable	Modify the collection and care about its size.
ICollection<T>	Defines methods to manipulate generic collections.	System.Collections.Generic.ICollection	IEnumerable<T>
IList	1.      Adding/  removing elements 2.      Clear the collection. 3.      Handle  positioning of the elements 4.      Provides an object indexer to allow the user to access the collection  eg myList[elementIndex]	System.Collections	ICollection	Modify the collection and ordering and / or positioning of the elements in the collection.
IList<T>	Some new methods for accessing a collection with specific positioning are present.	System.Collections.Generic	ICollection<T>
List	Dynamically resize arrays	System.Collections	IList	Ideal for linear collections not accessed by keys
List<T>	1.      Add  items 2.      Use an equality comparer 3.      accepts null as a valid value for reference types   4.      Allows duplicate elements. 5.      Type safe than ArrayList	System.Collections.Generic	IList<T>	Never have own member implementations with the concrete type List/List<T>.

C# IEnumerable

• IEnumerable is an interface.
• It is returned from query expressions.
• It implements the GetEnumerator method.
• It enables the facility to use foreach-loop.
• It permits the use of extension methods in the System.Linq namespace.
• ToList and ToArray conversion is possible to an IEnumerable instance.
   

In the following example the Display method accepts a list of names as arguments and displays them in the Console

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

 

 

 

class Program

{

    static void Main()

    {

            Display(new List<string> { "Anu", "James", "Sam" });

    }

 

    static void Display(IEnumerable<string> names)

    {

            foreach (string value in names)

                Console.WriteLine(value);

    }

}

 

 

The same example is modified to accept a list of array values as arguments

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using IEnuExample1;

 

 

 

class Program

{

    static void Main()

    {

        string[] names = new string[] { "Anu", "James", "Sam" };

 

        Display(names);

 

 

    }

 

    static void Display(IEnumerable<string> namesArg)

    {

            foreach (string value in namesArg)

                Console.WriteLine(value);

    }

}

 

The following example  convert object data into a List instance:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

 

namespace EnumEx2

{

  

 

class Program

{

    static void Main()

    {

                    //

                    // Use this input string[] array.

                    // ... Convert it to a List with the ToList extension.

                    //

                    string[] array = new string[]

                    {

                        "Anu", "James", "Sam"

                    };

                    List<string> list = array.ToList();

                    //

                    // Display the list.

                    //

          

 

                    foreach (string value in list)

                    {

                        Console.WriteLine(value);

                    }

    }

}

 

}

 

The following example sorts names using the LINQ syntax and displays these sorted elements in an array variable:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

 

namespace EnumExample3

{

 

 

    class Program

    {

        static void Main()

        {

            //

            // Use this input string[] array.

            // ... Convert it to a List with the ToList extension.

            //

            string[] array = new string[]

                    {

                        "James", "Sam", "Anu"

                    };

 

            // Use query expression on array.

            //

            var query = from element in array

                        orderby element

                        select element;

 

            Console.WriteLine(array.Count());

 

            string[] array2 = query.ToArray();

            //

            // Display array.

            //

            foreach (string value in array2)

            {

                Console.WriteLine(value);

            }

 

        }

    }

 

}