Parameters in Depth

Pass-by-value

• A copy of a variable is passed to the method.

• Any changes made to the value within the method does not affect the value outside of it.

static void Main(string[] args)
{
    int num = 15;
    Console.WriteLine("Number (outside the function): {0}", num);
    PrintSquare(num);
    Console.WriteLine("Number (outside the function): {0}", num);
    Console.Read();
}

static void PrintSquare(int number)
{
    number = number * number;
    Console.WriteLine("Number (inside the function): {0}", number);
}

Output:
-------
Number (outside the function): 15
Number (inside the function): 225
Number (outside the function): 15

Pass-by-reference

• A reference to a variable is passed.

  • The ref keyword is used

• If the value is changed within the method, it will be changed outside as well.

static void Main(string[] args)
{
    int num = 15;
    Console.WriteLine("Number (outside the funcion): {0}", num);
    PrintSquare(ref num);
    Console.WriteLine("Number (outside the funcion): {0}", num);
    Console.Read();
}

static void PrintSquare(ref int number)
{
    number = number * number;
    Console.WriteLine("Number (inside the funcion): {0}", number);
}

Output:
-------
Number (outside the function): 15
Number (inside the function): 225
Number (outside the function): 225

Out-parameters

• An out parameter is used to take a value from inside-to-outside of a method.

  • Whereas a ref parameter works both ways.

• Especially useful when you need to return more than one value from a method.

• Any values assigned to the parameters outside of the method will be overwritten.

static void Main(string[] args)
{
    double radius = 15;
    GetDimensionsOfCircle(radius, out double diameter, out double area);
    Console.WriteLine("Radius: {0}, Diameter: {1}, Area: {2}", radius, diameter, area);
    Console.Read();
}

static void GetDimensionsOfCircle(double radius, out double diameter, out double area)
{
    diameter = radius * 2;
    area = Math.PI * radius * radius;
}

Output:
-------
Radius: 15, Diameter: 30, Area: 706.8583470577034

Default Parameters

• A default value for select parameters can be passed

• Any non-default parameters must come before default parameters in the method definition

static void Main(string[] args)
{
    int w = 5;
    int h = 7;
    Console.WriteLine("W: {0}, H: {1}, ==> Area: {2}", w, h, GetAreaOfSquareOrRectangle(w, h));
    Console.WriteLine("W: {0}, H: {1}, ==> Area: {2}", w, 0, GetAreaOfSquareOrRectangle(w));
    Console.Read();
}

static int GetAreaOfSquareOrRectangle(int width, int height = 0)
{
    if (height == 0)
    {
        return width * width;
    }
    else
    {
        return width * height;
    }
}

Output:
-------
W: 5, H: 7, ==> Area: 35
W: 5, H: 0, ==> Area: 25