Basic C#

Question: What is the difference between Class and Structure (Struct)?

Ans: 1) structure: - In structure have a by default public. 

                       In class have a by default private.

       2) Structure cannot be inherited.

          But class can be Inherit.

       3) There is no data hiding features comes with structures. 

          Classes do, private, protected and public.

       4) A structure can't be abstract, 

          A class can be abstract.

       5) A structure is a value type, 

          While a class is a reference type.

       6) A structure is contain only data member,

          But class contains data member and member function.

       7) In a Structure we can't initiates the value to the variable

          But in class variable we assign the values.

       8) Structure are value type, they are stored as a stack on memory.  Whereas class is reference type, they are stored as heap on memory.

Question: Difference between abstract class and interface. 

       Ans:

§  Abstract class defines few or none of the methods, but interface defines all the methods.

§  Abstract classes should have subclasses else that will be useless, but Interfaces must have         implementations by other classes else that will be useless.

§  Only an interface can extend another interface, but any class can extend an abstract class.

§  All variable in interfaces are final by default.

·         Accessibility modifier (Public/Private/internal) is allowed for abstract class, but Interface   doesn’t allow accessibility modifier

·         Class can inherit only one abstract class can implement more than one interface.

·         Cannot create instance of abstract class.

Question: What is the Difference between Overriding and overloading?

Ans:         Overloading-------

·     Having same method name with different signatures.

·     Overloading does not take return type to differentiate overloaded method.

·     Method can be different  access modifier(public, private, protected) 

Ex:

Int add (int a, int b)

Int add (float a, float b)

                                         Are overloaded methods

                   Overriding--------

§  Methods name and signatures must be same.

§  Overriding comes with inheritance concept here parent and child both contains the same method. 

§  When execution takes place; child's method is called.

§  It use for implementing the Inheritance concept.

§  Redefine the base class method in drive class; method name and signature both are same.

§  Method must be public.

        Question: what is the difference between value types and reference types?

          Ans:

                      Value Type…….

§  Value type - bool, byte, decimal, double, enum, float, int, long, short, strut, uint, ulong

§  Value types are stored in the Stack

§  Value types directly contain their data, and instances of value types are either         allocated on the stack or allocated inline in a structure. 

§  Value types can be built-in (implemented by the runtime), user-defined, or enumerations. 

                        Reference Type…….                               

§  Class, delegate, interface, object & string are reference type.

§  Reference types are stored in the Heap.

§  Reference types store a reference to the value's memory address, and allocated on the heap. 

§  Reference types can be self-describing types, pointer types, or interface types. 

§  The type of a reference type can be determined from values of self-describing types.

§  Self-describing types are further split into arrays and class types. The class types are user-defined classes, boxed value types, and delegates.