out keyword in C#

Question

Hi All When i am executing the below below program I am getting the output as 10 while i am not assigning the val1 to i. So can anybody tell me plz why it is happening? class Class1 { int i; int Method1( out int val1) { val1 = 10; return i; } public static void Main( String [] args) { int x; Class1 cls = new Class1 (); cls.Method1( out x); Console .WriteLine(x); Console .ReadLine(); } } v

Vulpes · Answer

When a method has an 'out' parameter you're guaranteed that whatever variable is passed to the parameter will be assigned a value before the method returns. In this case you have a method (Method1) which takes an 'out' parameter (val1) of type int and also returns an int. The variable 'x' which is passed to val1 is assigned the value 10 within the method and consequently when the method returns x will still have that value. This line: Console.WriteLine(x); therefore prints 10 to the console. The method also returns the value of the field 'i' which is 0 (its default value) because no other value has been assigned to it. If you wanted 'i' to have the same value as val1 you'd need to change Method1 to this: int Method1(out int val1) { val1 = 10; i = val1; return i; } To obtain the return value you need to change your Main method to this: public static void Main(String[] args) { int x; Class1 cls = new Class1(); int y = cls.Method1(out x); Console.WriteLine(x); Console.WriteLine(y); // 0 or 10 if you've made the above change Console.ReadLine(); }