passing parameters in C#

Question

What i knew about 'out' parameter in c# is that if we want to return more than one from a single routine. But we can use 'ref' to return more than one from a single routine.Ofcourse ' out ' parameter also passed as reference variable. Then what is the need of 'OUT' ? where exactly we need 'out'? Please explain with real time situation.

Vulpes · Answer

As you say an 'out' parameter can be used if you want to return more than one value from a method though a 'ref' parameter can be used for the same purpose. However you'd generally prefer 'out' to 'ref' if you don't want to have to assign a value to the 'out' parameter first (with 'ref' you have to assign a value). With an 'out' parameter the compiler guarantees that it will have been assigned a value (in all possible paths) before the method returns. There is no such guarantee with a 'ref' parameter which may come back from the method with the same value that it had to start with. A good example of an 'out' parameter in practice is the Int32.TryParse (string out int) method. This returns a bool value indicating whether the string was successfully parsed to an Int32 or not. A value is also returned in the 'out' parameter representing the result of a successful parse or 0 otherwise. So: int i j; bool isValid = int.TryParse(abc out i); // isValid is false and i is 0 bool isValid2 = int.TryParse(123 out j); // isValid2 is true and j is 123