Parameters as Reference

Using the ref keyword

In C-Sharp, it’s possible to pass arguments as reference, instead of values.

• The traditional way to pass an argument to a method parameter would result in a copy of the argument to be used inside the method. This is passing the parameter as a value (which will create a copy of it).

int number = 5;
 
static int SquareNumber(int number) => number * number;
 
Console.WriteLine(SquareNumber(number)); // Returns 25.
Console.WriteLine(number); // Returns 5, variable not changed.

• To pass a parameter as reference, use the ref keyword to declare the method and when calling it. This will reference the memory location of the variable. All changes made inside the code block will persist after calling the method.

int number = 5;
 
static void SquareNumber(ref int number)
{
    number = number * number;
    // Note: there're no return statements.
}
 
SquareNumber(ref number); // The change will be made directly to number.
 
Console.WriteLine(number); // Returns 25, change made to the variable.

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Using the out keyword

Similar to ref, out also passes a variable by reference. Using out, the variable doesn’t need to be initialized before the calling the method, but must be before exiting it. Using out, it’s possible to return multiple values from a single method.

int number = 5;
int numberSquared; // Not initialized.
 
static void SquareNumber(int number, out int squared)
{
    squared = number * number;  // Assigning value to variable.
}
 
SquareNumber(number, out numberSquared);
 
Console.WriteLine(numberSquared); // Returns 25

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