Introduction

  • The out keyword causes arguments to be passed by reference.
  • To use an out parameter, both the method definition and the calling method must explicitly use the out keyword.
  • Although variables passed as out arguments do not have to be initialized before being passed, the called method is required to assign a value before the method returns.

Example

Simple Program to check whether the given character exists or not,

  1. using System;
  3. class Program
  4. {
  5. static void Main ( )
  6. {
  7. bool sharpsymbol; // Used as out parameter.
  8. bool AndSymbol;
  9. bool Paranthesis;
  10. const string value = "& # @";// Used as input string.
  12. CheckString ( value, out sharpsymbol, out AndSymbol, out Paranthesis );
  14. Console.WriteLine ( value ); // Display value.
  15. Console.Write ( "sharpsymbol: " ); // Display labels and bools.
  16. Console.WriteLine ( sharpsymbol );
  17. Console.Write ( "AndSymbol: " );
  18. Console.WriteLine ( AndSymbol );
  19. Console.Write ( "Paranthesis: " );
  20. Console.WriteLine ( Paranthesis );
  21. Console.ReadLine ( );
  22. }
  24. static void CheckString ( string value,
  25. out bool sharpsymbol,
  26. out bool AndSymbol,
  27. out bool Paranthesis )
  28. {
  29. // Assign all out parameters to false.
  32. sharpsymbol = AndSymbol = Paranthesis = false;
  34. for(int i = 0; i < value.Length; i++)
  35. {
  36. switch(value[i])
  37. {
  38. case '#':
  39. {
  40. sharpsymbol = true; // Set out parameter.
  41. break;
  42. }
  43. case '&':
  44. {
  45. AndSymbol = true; // Set out parameter.
  46. break;
  47. }
  48. case '(':
  49. {
  50. Paranthesis = false; // Set out parameter.
  51. break;
  52. }
  53. }
  54. }
  55. }
  56. }
Output

Output

When the Problem Occurs.

code

Note

In the above program, even though you assigned the out variable value inside the looping/case statement, if you don't assign any value in the method definition like the above snagit then you will get the following error:

error

Conclusion

I hope the above information is useful for beginners, kindly let me know your thoughts.