C# Basic Interview Question

Q: what are different version of c# and their framework support  ?
Ans : c#1.0 ,1.2,2.0,3.0,4.0,5. and 6.0 are different version of c# .
 Frame work  - dot net version
 .Net Framework 1.0  =  c#1.0  visual studio 2002
 .Net Framework 1.1   = c#1.2 Visual studio 2003
 .Net Framework 2.0  =  c# 2.0    = visual studio 2005
 .Net Framework 2.0 ,3.0, 3.5   =  c#3.0 =  visual studio 2008 , visual studio 2010
 .Net Framework 4.0  = c#4.0   visual studio 2010
 .Net Framework 4.5  = c#5.0  = visual studio 2012, 2013
 .Net Framework 4.6  = c#6.0  = visual studio 2015


Q : what are method in c# ?
Ans : Method or function(will have return type) will be used  for writing a programme in more manageable way ,
syntax for methods  :

 [attribute]
  access-modifiers  return type  method name(parameter)
   {
      //body
   }

Method can be declare in two type  1 : Instance  2 : Static ,

for declaring  a method as static use keyword static in method e.g.
public static void hello()
  {
     // body
  }
  for static we do not need instance or can say new keyword for calling them in Main method ,that is also a static method .


Q : what the parameter we used in method  ?
Ans : there are 4 types of parameter used in method
   1: value type  2: reference type 3:  out parameter  4:  arrays type .

Q : what is difference between concrete class and abstract classes ?
Ans :  concrete class and abstract class are same in all virtue except that abstract class can not be initiated while concrete class class can be initiated .
   

Q: How to declare array in c# ?
Ans : very Basic way of declaring a array is to use [] sign  after your datatype  eg int[]
array is basically used for storing similar type of values . suppose i want to store three integer type in array ,then we can write like this int[] x  = new int[3] . now passed value to your integer by using
x[0] = 1 , x[1] = 23, x[2] = 56 . arrays always start from 0 . arrays are strongly typed means once you have defined x as integer , now you can not store string value in the array  , also there is drawback of array once you have initiated array with defined value now you can not grow or decrease array area , like in our example you can not grow or decrease by 3 .


Q : How to write switch statement  ?
Ans :  Switch is basically an alternate to if ,else condition , if you do not want to check many condition through ,if else situation .
syntax for switch statement :

switch( input)
{
    Case  input1:
        console.writeLIne (you have entered input1);
       break;
     case input :
        console.writeLine(you have entered input);
       break ;
     default :
      console.writelLIne(you have entered nothing);
      break;
}

so in above case ,it will print "you have entered input" , default  is necessary  as last condition , break is  also necessary after each condition  to break the statement ,once it is satisfying condition .it will not go to next  condition .

Q : how to use while condition in c# ?
Ans : syntax for while loop is

while(condition)
{
   // do something ;
}
now suppose i want to print some values  through while statement ,then it will look like this

int x  = 0

while( x < 10)
{
  console.write( x) ;
   x  = x+ 2 ;
}
so  it will print like 0, 2 ,4 6,8


Q :  how to use do while loop  ?
Ans :  in do while  statement syntax  :
     do
   {
       //something
    }while(condition)

   like taking reference from above example ,
int x = 0 ;
do
 {
     console.Writeline (x) ;
     x  = x+ 2 ;
 }while(x< 10)

the difference between ,while loop and do -while loop is that  , in while condition if condition is false it will not execute statement, but in do-while at least a single time statement will executed if statement  is false .

Q : what is foreach loop  ?
Ans :  for each loop can be used with arrays , collection ,generics ,arraylist to iterate though the items .
syntax for foreach loop

foreach (int x in  array)
 {
     console.writeline (x) ;
 }

so here it will print all stored values of array  .

Q :   What are interface in c#  ?
Ans :
Interface are declared in c# by using interface keyword,
Interface allowed multiple inheritance .
For using interface a class must provide implementation of interface  for using it .
A interface can inherit any other interface .
A interface is public by default .  A
interface can not be used by creating a instance  .
we can using a interface variable by assigning the child class who is inheriting interface mean interface i  = new childclass();

Q : what are abstract classes  ?
Ans :
Abstract Class can not not be initiated and only work like as base class .
Abstract class may contain abstract member .
Abstract can not be  sealed class .
A class inherited from abstract must provide implementation by using override keyword to all inherited members .or declared abstract to self for using abstract class .


Q what are difference between abstract and interface    ?
Ans :
1 : Interface can not have implementation  ,while abstract class can have implementation .
2 :  A interface can only be inherited by another interface ,while abstract class can be inherited by interface or abstract class as well .
3:  Multiple inheritance is possible in interface while in abstract class it is not .
4:   Interface is by default public ,while abstract class need access modifier .

Q : what are delegate  ?
Ans :Delegate are function pointer , it is similar like method declaration except it used delegate keyword to self

Public delegate void iamdelegate(string test) ;

public static void  delegate_method(string mssg)
 {
    console.write line (mssg) ;
 }

so for using this delegate  in main method ,you need to invoke delegate like
         iamdelegate x = new iamdelegate(delegate_method) ;
          x("Print this");