Once a component is designed it can be reused from any kind of application like in console application or windows application or web application or device application etc.
Once a component is designed in any programming language of .net it can be reused from any other programming languages of .Net; i.e., .Net components or assemblies will provide language interoperability.
To create components in .Net, we use class library templates.

End user will never interact with some applications; but will interact with components or DLL.
Program for creating a Component / Assembly
  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. namespace CLibMaths
  6. {
  7. public class Arithmatic
  8. {
  9. public int Num1, Num2, Result;
  10. public int PNum1
  11. {
  12. set {
  13. Num1 = value;
  14. }
  15. get {
  16. return Num1;
  17. }
  18. }
  19. public int PNum2 {
  20. set {
  21. Num2 = value;
  22. }
  23. }
  24. public int PResult {
  25. get {
  26. return Result;
  27. }
  28. }
  29. public int Add() {
  30. Result = Num1 + Num2;
  31. return Result;
  32. }
  33. public void Subtract() {
  34. Result = Num1 - Num2;
  35. }
  36. public void Multiply() {
  37. Result = Num1 * Num2;
  38. }
  39. public void Divide() {
  40. Result = Num1 / Num2;
  41. }
  42. }
  43. }
ADD a new class with name ClsMathNumbers

Change the accessibility of the class to public and write following code.
  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. namespace CLibMaths
  6. {
  7. public class ClsMathNumbers
  8. {
  9. public int Square(int x) {
  10. return x * x;
  11. }
  12. public int Cube(int x) {
  13. return x * Square(x);
  14. }
  15. public int Factorial(int x) {
  16. int R = 1;
  17. for (int i = 1; i <= x; i++) {
  18. R = R * i;
  19. }
  20. return R;
  21. }
  22. }
  23. }
Building the solution will create a DLL. this dll is known as .net component. To see the DLL go to the \bin\Debug folder of the application , you find the CLibMaths.dll.