Saturday, 19 September 2015

Method Overloading And Method OverRiding

Method Overloading refers to Concept the defining the one or more functions or methods with same name with different Parameter Length or Parameter Types . So Functions are differenciated by their signature or Parameters .

Example For Method OverLoading

//Overloading
public class test
{
    public void getStuff(int id)
    {}
    public void getStuff(string name)
    {}
}
 
Method OverRiding is Totally Different Concept As Compared to Method Overloading . Method OverRiding Refers to Redefining the Function that Correspond to Some Other Class and Accessed Using Inheritance .

The Concept of Method OverRiding depends on Two Keywords - Virtual and OverRide

In Simple Scenario to Explain Method OverRiding with Example is Lets Assume We have a Base Class with function Sample() in Base Class then The Oher class that Derived From that Base Class Can Redefine the Functionality of That Sample() Function refers to Concept of Method OverRiding .

Example1  For Method OverRiding

class BC
{
  public virtual void Display()
  {
     System.Console.WriteLine("BC::Display");
  }
}

class DC : BC
{
  public override void Display()
  {
     System.Console.WriteLine("DC::Display");
  }
}

class Demo
{
  public static void Main()
  {
     BC b;
     b = new BC();
     b.Display();    

     b = new DC();
     b.Display();    
  }
}

Output

BC::Display
DC::Display
 

Example1  For Method OverRiding

//Overriding
public class test
{
        public virtual getStuff(int id)
        {
            //Get stuff default location
        }
}

public class test2 : test
{
        public override getStuff(int id)
        {
            //base.getStuff(id);
            //or - Get stuff new location
        }
}

 

 

Value Types Vs Reference Types Dotnet


Stack and heap

In order to understand stack and heap, let’s understand what actually happens in the below code internally.

public void Method1()
{
    // Line 1
    int i=4;

    // Line 2
    int y=2;

    //Line 3
    class1 cls1 = new class1();
}


It’s a three line code, let’s understand line by line how things execute internally.
  • Line 1: When this line is executed, the compiler allocates a small amount of memory in the stack. The stack is responsible for keeping track of the running memory needed in your application.
  • Line 2: Now the execution moves to the next step. As the name says stack, it stacks this memory allocation on top of the first memory allocation. You can think about stack as a series of compartments or boxes put on top of each other.
  • Memory allocation and de-allocation is done using LIFO (Last In First Out) logic. In other words memory is allocated and de-allocated at only one end of the memory, i.e., top of the stack.
  • Line 3: In line 3, we have created an object. When this line is executed it creates a pointer on the stack and the actual object is stored in a different type of memory location called ‘Heap’. ‘Heap’ does not track running memory, it’s just a pile of objects which can be reached at any moment of time. Heap is used for dynamic memory allocation.

Why String Are Value Types Csharp Dotnet


The distinction between reference types and value types are basically a performance tradeoff in the design of the language. Reference types have some overhead on construction and destruction and garbage collection, because they are created on the heap. Value types on the other hand have overhead on method calls , because the whole object is copied rather than just a pointer.

Because strings can be  much larger than the size of a pointer, they are designed as reference types. Also, as Servy pointed out, the size of a value type must be known at compile time, which is not always the case for strings.

Strings aren't value types since they can be huge, and need to be stored on the heap. Value types are stored on the stack. Stack allocating strings would break all sorts of things: the stack is only 1MB, you'd have to box each string, incurring a copy penalty, you couldn't intern strings, and memory usage would balloon, etc

That is why a string is really immutable because when you change it even if it is of the same size the compiler doesn't know that and has to allocate a new array and assign characters to the positions in the array. It makes sense if you think of strings as a way that languages protect you from having to allocate memory on the fly 

Boxing And Unboxing in DotNet

Boxing and unboxing

I Recommend to Go to this link to Read about Value Types and Reference Types Before Going To Understand the concept of Boxing and Unboxing

Value Types Vs Reference Types Dotnet
http://geeksprogrammings.blogspot.in/2015/09/value-types-vs-reference-types-dotnet.html

Boxing and unboxing are the most important concepts you always get asked in your interviews. Actually, it's really easy to understand, and simply refers to the allocation of a value type (e.g. int, char, etc.) on the heap rather than the stack.

Boxing

Implicit conversion of a value type (int, char etc.) to a reference type (object), is known as Boxing. In boxing process, a value type is being allocated on the heap rather than the stack.

Unboxing

Explicit conversion of same reference type (which is being created by boxing process); back to a value type is known as unboxing. In unboxing process, boxed value type is unboxed from the heap and assigned to a value type which is being allocated on the stack.

For Example
    // int (value type) is created on the Stack
    int stackVar = 12;
    
    // Boxing = int is created on the Heap (reference type)
    object boxedVar = stackVar;
    
    // Unboxing = boxed int is unboxed from the heap and assigned to an int stack variable
    int unBoxed = (int)boxedVar;


Real Life Example

    int Val_Var = 10;
    ArrayList arrlist = new ArrayList();
    
    //ArrayList contains object type value
    //So, int i is being created on heap
    arrlist.Add(Val_Var); // Boxing occurs automatically Because we are Converting int to Object Type This is Called Boxing
    
    int j = (int)arrlist[0]; // Unboxing occurs

Performance implication of boxing and unboxing

In order to see how the performance is impacted, we ran the below two functions 10,000 times. One function has boxing and the other function is simple. We used a stop watch object to monitor the time taken.
The boxing function was executed in 3542 ms while without boxing, the code was executed in 2477 ms. In other words try to avoid boxing and unboxing. In a project where you need boxing and unboxing, use it when it’s absolutely necessary.

Boxing And Unboxing in DotNet
Boxing And Unboxing in DotNet