what is dll in c#.net

Structure is a user defined type which can contain different member (variable, method and property etc). 
Class is  a user define type which can contain such type of member but there is some difference between structure and class.
Now i am going to implement structure and class in C# after that i will show you exact difference betweenstructure and class in C#.
There are some steps please follow them step by step which is given below.

Step 1 First open your visual studio->File->New->project->console Application->OK->Now write the following code which is given below in step 2.
Step 2 structure and class program code:-
see it:-

01	using System;

02	namespace structure

03

{

04	class Program

05

{

06	public struct student

07

{

08	public String sname;

09	public int sage;

10	public student(String s,int i)

11

{

12

sname=s;

13

sage=i;

14	Console.WriteLine("student name is"+" " + sname);

15	Console.WriteLine("student age is"+ " " + sage);

16	Console.ReadLine();

17

18

}

19	public void show()

20

{

21	Console.WriteLine("student name is" + " " + sname);

22	Console.WriteLine("student age is" + " " + sage);

23	Console.ReadLine();

24

}

25	public class employee

26

{

27	public String ename;

28	public int eage;

29

30	public employee()

31

{

32	ename="santosh";

33

eage =24;

34

}

35	public employee(String e, int j)

36

{

37

ename=e;

38

eage=j;

39	Console.WriteLine("employee name(parameter department) is"+" " + ename);

40	Console.WriteLine("employee age(parameter department) is" + " " + eage);

41	Console.ReadLine();

42

}

43	public void display()

44

{

45	Console.WriteLine("employee name is" + " " + ename);

46	Console.WriteLine("employee age is" + " " + eage);

47	Console.ReadLine();

48

}

49

}

50	static void Main(string[] args)

51	{  //calling the structure member

52	student st = new student("ram", 23);

53	st.sname = "vinod";

54	st.sage = 22;

55	st.show();

56

57	//calling the class member paramerized cosntructur

58	employee em = new employee("shayam", 33);

59	em.ename = "Rajesh";

60	em.eage = 21;

61	em.display();

62

63	//calling the class member empty costructur

64	employee em1 = new employee();

65	em1.display();

66

67

}

68

}

69

}

70

}

Step 3 Now  Run the program(press F5).
See output:

Description:- Now i am going to explain how these  above program will work.Please read each point to understand the whole concept of this program.

1. First i have created a structure student with struct keyword.
2. After that i have declared and defined following member of student structure which is give below.

• I have declared two variable sname and sage .
• I have created a constructor with two parameter.
• I have created a show() method for displaying the student  member data.

     3. After that i have created a class employee.
     4. After that i have declared and defined following member of employee class which is give below.

•     I have declared two variable ename and eage .
• I have created a constructor with No parameter.
• I have created a constructor with two parameter.
• I have created a display() method for displaying the employee  member data.

      5. After that i have created object of student structure and passed two parameter(at the object creation) in themain method.

   EX1.

student st=new student("ram",23);

Explanation:-

here parameterized  constructor of student structure will call and copy the values in corresponding variables.

           s<--ram

           i<--23

           sname<--ram

            sage<--23

output:

student name is ram

student age is 23

EX2:
Now again ,i have assigned values in variable of student sname and sage with the help of object st.
st.sname="vinod";
st.sage=22;
st.show();

here i have called the show() method of student to display the sname and sage values.
output:

student name is  vinod

student age is  22

     6. After that i have created the object of employee class and passed two parameter(at object creation ).
EX1:
employee em =new employee("shayam",33);
Explanation:-
here parameterized  constructor of employee class will call and display the parameter values.

          e<--shayam

           j<--33

           sname<--shyam

            sage<--33

output:
employee name(parameter department) is shayam
employee age(parameter department) is 33
EX2:

Now again ,i have assigned values in variable of employee ename and eage with the help of object em.
em.ename="Rajesh";
em.eage=21;
st.display();
here i have called the display() method of employee class to display the ename and eage values.
output:
employee name is Rajesh
employee age is 21

     7.  After that i have called empty constructor of employee class by creating the object of employee classagain for calling the empty constructor of the employee class. 

employee em1 =new employee();
em1.display();
output:
employee name is Santosh
employee age is 24
 Difference between Structure and class :-

• Structure is stored within stack memory and Class is stored within heap memory.
• In Structure we can not define parameter less constructor but in class can do it.
• In structure we can not initialize the data member at declaration but in class can do it. 
• In structure inheritance is not possible(one structure can not inherited to another structure )but in class it is possible.
• We can not declare virtual override and abstract keyword with structure but in class it is possible.
• Class is Reference type but structure is value type.
• We can use Destructor in Class but not in Structure.