# Changing Roles

Through the day, people treat Chloe as a student, a singer or an athlete. Each sees only the role it needs. Polymorphism shifts focus in the same way.

Apprentice · C# · OOP · Updated November 3, 2026

## After this lesson you can

- Explain how treating an object as one of its forms limits what you can ask it to do

## Key takeaways

- Seeing an object as one of its forms means asking only what that form can do. The object itself doesn't change.
- Code that holds an `Archer` as a `Character` can ask for `Attack`, `TakeDamage` and `LevelUp`, but not `AddArrow`.
- The type you hold an object as decides what you can ask of it; the object itself decides how it does it.

Through each day, Chloe goes from class, to rehearsal with the drama club, to an intense volleyball practice.

![Chloe on her way through a busy day](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/09/8378c8f669314f288a4c0938d1462f82.png "Chloe on her way through a busy day")

## Scholar

In class, her teacher treats her as a **student**. She's expected to study, and to take tests.

## Singer

![Chloe singing on stage](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/09/630e568350cc4e8e9afc2b7d5e79dd0b.png "Chloe singing on stage")

At rehearsal, she's a **singer**. She's expected to know her part, to sing it, and to remember her lines.

## Athlete

![Chloe playing volleyball](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/09/b3f3b07edb62480782f26667669f0a42.png "Chloe playing volleyball")

At volleyball, her teammates count on her as an **athlete**. She needs to serve well and hit hard.

## Each role sees only part of her

When the teacher hands out a test, Chloe can still sing and still play volleyball. But the teacher is only thinking of her as a student, so the teacher only asks student things of her: study, take the test. Asking her to serve a volleyball in the middle of math class would make no sense.

That's the heart of polymorphism: **you focus on the form that matters right now, and ignore the rest.** The object doesn't change; what you're looking at does.

## The same in code

When code holds an `Archer` as a `Character`, it can only ask for what every character can do:

| Seen as | You can ask it to | You can't ask it to |
|---|---|---|
| `Character` | `Attack`, `TakeDamage`, `LevelUp` | `AddArrow`: not every character has arrows |
| `Archer` | Everything a character can do, plus `AddArrow` | |

The archer still has its arrows. But code that only knows it as a character can't count on arrows, because a wizard or a knight wouldn't have any.

## Check yourself

1 question to try on the lesson page.

## So what

Each role sees only the part of an object it needs. In C#, the type you hold an object as decides what you can ask of it, and the object itself decides how it does it.

## Key terms

- [Polymorphism](https://www.ask-codey.com/glossary/polymorphism-oop)

## Cheat sheets

- [Polymorphism in C#](https://www.ask-codey.com/cheat-sheets/polymorphism-in-csharp-an-overview-cheat-sheet)

Source: https://www.ask-codey.com/lessons/polymorphism-in-csharp-changing-roles