C# Learnings Today

Revising C#. Yea I'm revising my C# basics. In this post we would discuss on

•  Interfaces
•  Generics
•  LINQ
• Threading in C# 

Value Type Vs Reference Type

• Value Types - Stored in stack (int, float, double, decimal..)
• Reference Type - Data Stored in Heap, Reference stored in Stack (Class, Interface, array, delegate)

Why Interfaces ?

• Define methods but not implement them (Reference Type)
• Cannot have Members 
• Can Inherit Interfaces

Abstract Classes

• Can contain regular, abstract and non abstract members
• Cannot create instances of abstract classes
• Abstract class can be derived from other abstract classes

When to use an Abstract Class and an Interface

• Use an abstract class to provide default behavior
• Abstract Class - creating a class library which will be widely distributed or reused
• Use an interface to design a polymorphic hierarchy for value types  

Example

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

//Interface Example

interface IExample

{

    //Method Defined, Not Implemented

    int TestInterfaceMethod(int a, int b);

}

class MyTest : IExample

{

    public int TestInterfaceMethod(int a, int b)

    {

        return (a + b);

    }

}

abstract class abstractClassExample

{

    //Has both abstract and non abstract methods

    public void BaseMethod()

    {

           Console.WriteLine("I am Base Class");

    }

    abstract public void AbstractBaseMethod();

}

class ChildClass : abstractClassExample

{

    //Implement abstract method

    override public void AbstractBaseMethod()

    {

        Console.WriteLine("Child Class OverWritten");

    } 

}

class Program

{

    static void Main()

    {

        MyTest M = new MyTest();

        Console.WriteLine(M.TestInterfaceMethod(5, 10));

        ChildClass CC = new ChildClass();

        CC.BaseMethod();

        CC.AbstractBaseMethod();

        Console.ReadKey();

    }

}

Output

Why Generics ?

• Allow you to execute code for multiple data types

System.Collections.Generic just like:
List<T>
Dictionary<K, V>
Queue<T>
Stack<T>
How do C# generics compare to C++ templates?

Why LINQ ?

• Language Integrated Query
• Query on data collection similar to sql query to databases

Why I should use Linq?
When should we use LINQ?
LINQ: Introducing The Skip Last Operators
SQL Bits Session - LINQ for DBAs and SQL Developers
LINQ Notes

Threading in C#
C# - Use of Multithread (when) - (Stack Overflow Question - Reposting it)

• You can use threads when you need different execution paths
• Allowing requests to be processed simultaneously
• Making efficient use of an otherwise blocked CPU 

What is the difference between Deep Copy and Shallow Copy

• Reposting it from msdn question
• For instance, a Person object, containing references to an Address object, several Phone objects, etc.
• If you make a shallow copy of that Person object you now have two Person objects, but they share the Address objects and Phone objects. In other words, you only make a new Person object, and then link it up to the existing Address and Phone objects.
• A deep copy, on the other hand, will make new copies of everything, so that both Person objects now have their own set of Address and Phone objects. 

When is a shallow copy desirable (instead of a deep copy)? (Stack Overflow Question - Reposting it)

• In C++, you might use deep copying to avoid difficult memory management issues
• In Java/.NET, deep copying is not necessary for those reasons. Since the languages are both garbage collected

Static Methods Example
Still remember c basics. They still seem to hold true. Tested below code

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication1

{

    class Program

    {

        static int i=0;

        static void TestMethod()

        {

            //only one copy exists throught the program

            //last modified value used in this case

            i++;

            Console.WriteLine("Value of it is " + i);

            Console.ReadKey();

        }

        void TestforValueMethod()

        {

            //Local variable hides global variable

            int i=0;

            Console.WriteLine("Value of i is " + i);

            i++;

            Console.ReadKey();

        }

        static void Main(string[] args)

        {

            //static method invoking without class creation

            TestMethod();

            TestMethod();

            TestMethod();

            Console.ReadKey();

            Program p = new Program();

            p.TestforValueMethod();

            TestMethod();

            Console.ReadKey();

           

        }

    }

}

Output is

More Reads
What is the difference between Arraylist.Copy() vs Arraylist.Clone()
ADO.NET: Building a Custom Data Provider for Use with the .NET Data Access Framework

Very Good Article Series for .NET Test Automation Series
I recommend Illustrated C# 2010 book. Awesome book.

Happy Reading!!