Methods and parameters

In plain English

A method groups a reusable block of code behind a name, and its return type declares what it gives back. void returns nothing, while a concrete type promises a value. Optional parameters supply defaults, and named arguments let you skip or reorder them. out and ref pass arguments by reference so a method can return extra values, and overloading lets one method name have several signatures.

Step by step

1. 1Write a method with a return type and call it.
2. 2Add an optional parameter and call with a named argument.
3. 3Add an overload with a different parameter list.
4. 4Use out and ref to return extra values.

public class Lesson
{
    public string Describe(string title, int minutes = 10)
    {
        return title + " takes " + minutes + " minutes";
    }

    public string Describe(string title)
    {
        return "No duration set for " + title;
    }

    public void Track(string title, out int slot, ref int seen)
    {
        slot = seen;
        seen += 1;
    }
}

var lesson = new Lesson();
var summary = lesson.Describe("C#", minutes: 12);
var shortSummary = lesson.Describe("HTML");
int slot;
var seen = 0;
lesson.Track("C#", out slot, ref seen);
Console.WriteLine(summary);
Console.WriteLine(slot);

Common mistakes

• You cannot overload two methods that differ only in their return type.
• An out parameter must be assigned before the method returns.
• A ref argument must be initialized before it is passed in.
• Stacking too many optional parameters makes call sites hard to read.