# Exercise: Methods and Conditions

Write 13 methods for three small businesses, using parameters, return values and conditions, and check each one with tests.

Apprentice · C# · Updated October 30, 2026

Three small businesses need your help: a backyard basketball league, Claire's cookie shop, and Elliot's lawn-care business. Each needs a few calculations, and each calculation is a method for you to write. Tests check every method as you go.

## Get the exercise code

Open this lesson's GitHub repository, [github.com/ask-codey/exercise-methods-and-conditions](https://github.com/ask-codey/exercise-methods-and-conditions), also linked from the **Exercise** box beside the lesson. Click **Code**, then **Download ZIP**, and unzip it into your `bootcamp` folder. Or clone it with Git.

The folder holds two projects:

- `MethodsExercise`: your code. Each business is a class of methods in its own file: `BackyardBasketball.cs`, `ClairesCookies.cs` and `ElliotsYardCare.cs`.
- `MethodsExercise.Tests`: the tests that check your methods. You don't need to change these.

Open `MethodsExercise.slnx` in Visual Studio, or open the folder in VS Code.

## What to do

Every method is already declared, with its parameters and return type, and returns `0` for now. The comment above it says what it should return, with examples:

```csharp
/*
 * Return the percentage of games won, as a whole number.
 *
 * CalculateWinningPercentage(7, 3) -> 70
 * CalculateWinningPercentage(5, 5) -> 50
 */
public static int CalculateWinningPercentage(int gamesWon, int gamesLost)
{
    return 0;
}
```

Replace `return 0;` with your own code. The first line of each file, `namespace MethodsExercise;`, groups the project's code together; leave it as it is.

## Check your work

In Visual Studio, choose **Test > Run All Tests**. Or, in Git Bash, from the folder with the `.slnx` file:

```bash
dotnet test
```

At first almost every test fails. Each method you finish turns its tests green. When a test fails, its message says which values it used and what it expected, for example *A team with 5 wins and 10 losses has won 33% of its games.*

You can also try a method in `Program.cs` and run the project with **Ctrl+F5**.

## Hints

- **Work out an example by hand first.** If you can't get 33 from 5 wins and 10 losses with a calculator, code won't help yet.
- **Integer division drops the fraction.** `5 * 100 / 15` is `33`. Multiply before you divide.
- **`Math.Ceiling` rounds up and `Math.Round(value, 2)` rounds to cents.** You met both in *Arithmetic and Expressions in C#*.
- **Methods can call methods.** `CalculateProfit` needs the cost, and `CalculateCost` already works it out.
- **Write your own helper.** Three of Claire's methods add the same sales tax. A small method of your own, such as `AddTax(decimal subtotal)`, keeps that rule in one place.
- **Pick the right decision.** A true/false choice suits `?:` or `if`; a list of exact names suits a switch; ranges suit `if` and `else if`.

## When you're done

Every test is green. Read your code again, as if someone else wrote it: are the names clear? Is any calculation written twice? Tidy it up and run the tests again; they'll tell you if you broke anything.

## Submit your exercise

The exercise is how you finish this lesson. When your work is done, put it on GitHub in a repo of your own, then submit that repo's address here.

1. On GitHub, click **+**, then **New repository**. Name it (for example `exercise-methods-and-conditions`), choose **Public**, and click **Create repository**. Leave out the README: your folder already has one.
2. In a terminal in your exercise folder (Git Bash on Windows), send your work to your new repo. If you downloaded the ZIP:

   ```bash
   git init -b main
   git add .
   git commit -m "My solution"
   git remote add origin https://github.com/your-name/exercise-methods-and-conditions.git
   git push -u origin main
   ```

   If you cloned the starter instead, point your copy at your own repo, then commit and push:

   ```bash
   git remote set-url origin https://github.com/your-name/exercise-methods-and-conditions.git
   git add .
   git commit -m "My solution"
   git push -u origin main
   ```

3. Paste your repo's address, such as `https://github.com/your-name/exercise-methods-and-conditions`, into **Submit your exercise** on this page. The site checks that the repo is public and holds your commits, and then the lesson is complete.

Changed something after you submitted? Push it, and submit again: your latest submission is the one that counts.

## So what

These are the same steps every real feature takes: a method with a clear name, the values it needs, a decision or two, and tests that prove it works.

## Key terms

- [Method Parameter](https://www.ask-codey.com/glossary/method-parameter-c-sharp)
- [Return Value](https://www.ask-codey.com/glossary/return-value-c-sharp)
- [switch Expression](https://www.ask-codey.com/glossary/switch-expression)

## Related

- [Organizing Code into Methods](https://www.ask-codey.com/lessons/introduction-to-methods-organizing-code-into-methods)
- [If](https://www.ask-codey.com/lessons/conditional-logic-in-csharp-if)
- [Switch Expressions and the Conditional Operator](https://www.ask-codey.com/lessons/conditional-logic-in-csharp-switch-expressions)

Source: https://www.ask-codey.com/lessons/exercise-methods-and-conditions