C# Programming/Keywords/out

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The out keyword explicitly specifies that a variable should be passed by reference to a method, and set in that method. A variable using this keyword must not be intialized before the method call to ensure the developer understand its intended effects. Using this keyword requires the called method to set the variable using this modifier before returning. Using out also requires the developer to specify the keyword even in the calling code, to ensure that it is easily visible to developers reading the code that the variable will have its value changed elsewhere, which is useful when analyzing the program flow.

An example of passing a variable with out follows:

void CallingMethod()
{
    int i;
    SetDependingOnTime(out i);
    // i is now 10 before/at 12 am, or 20 after
}
 
void SetDependingOnTime(out int iValue)
{
    iValue = DateTime.Now.Hour <= 12 ? 10 : 20;
}


C# Keywords
abstract as base bool break
byte case catch char checked
class const continue decimal default
delegate do double else enum
event explicit extern false finally
fixed float for foreach
goto if implicit in int
interface internal is lock long
namespace new null object operator
out override params private protected
public readonly ref return sbyte
sealed short sizeof stackalloc
static string struct switch this
throw true try typeof uint
ulong unchecked unsafe ushort using
var virtual void volatile while
Special C# Identifiers
add alias get global partial
remove set value where yield