# Exercise: Strings

Build HTML and XML from strings, format and rearrange people's names, and try seven bonus word problems, with tests that check each method.

Apprentice · C# · Updated October 30, 2026

A full-stack developer turns data into text all day: HTML for web pages, XML and other formats for other programs, names and labels for people to read. In this exercise you'll write 15 methods that do exactly that, and tests check each one.

## Get the exercise code

Open this lesson's GitHub repository, [github.com/ask-codey/exercise-strings](https://github.com/ask-codey/exercise-strings), 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 `StringsExercise` project has three classes of methods:

| File | Methods |
|---|---|
| `Markup.cs` | `ChangeCase`, `CreateHtml`, `MoreHtml`, `CreateXml`, `FormattedXml` |
| `NameFormatter.cs` | `FormatFullName`, `CreateUserName`, `ReformatName` |
| `WordPlay.cs` (bonus) | `Initials`, `FileExtension`, `MaskCardNumber`, `CountVowels`, `IsPalindrome`, `Censor`, `TitleCase` |

`StringsExercise.Tests` holds the tests. Open `StringsExercise.slnx` in Visual Studio, or the folder in VS Code.

## What to do

Each method's comment says what it should return, with examples. Replace the `return` line with your own code, then run the tests with **Test > Run All Tests**, or `dotnet test` in Git Bash. Do `Markup.cs` and `NameFormatter.cs` first; `WordPlay.cs` is for when you want more.

## A little HTML and XML

You'll meet HTML properly later in the course. For now you only need its shape: an **element** is a name in angle brackets, `<p>`, then its content, then the same name with a slash, `</p>`:

```text
<p>This is a paragraph</p>
<strong>Bold text</strong>
<p />
```

XML has the same shape, but you choose the names to describe your data, such as `<customer>` and `<name>`. In XML, an element with no content can close itself, like the last line. HTML allows that only for empty elements such as `<br>` and `<img>`; a real web page writes `<p></p>`. This exercise uses the XML way.

## Hints

- **Interpolation** makes markup easy to read: `$"<{elementName}>{content}</{elementName}>"`.
- **New lines** in a string are `\n`. In `FormattedXml`, the indent is two spaces.
- **Optional parts:** check for `""` before you add a middle name or a suffix, so no double spaces or stray commas appear.
- **Names:** `Split(' ')` turns `"Glen Carter Williamson"` into three words. A word's first letter is `word[0]`.
- **After a comma:** `IndexOf(',')` finds it (or returns `-1`), and `Substring` cuts the name there.
- **Reuse:** `MoreHtml` can call `CreateHtml` for elements that have content.

## When you're done

Every test is green. Read your methods once more: is there a long chain of `+` that interpolation would make clearer? A repeated step a small method could hold?

## 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-strings`), 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-strings.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-strings.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-strings`, 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

Turning data into well-formed text, whether markup, usernames or display names, is one of the most common jobs in web development, and it's all built from a few string methods.

## Key terms

- [String Interpolation](https://www.ask-codey.com/glossary/string-interpolation-c-sharp)
- [Escape Sequence](https://www.ask-codey.com/glossary/escape-sequence-c-sharp)
- [Substring()](https://www.ask-codey.com/glossary/substring-c-sharp)
- [Split()](https://www.ask-codey.com/glossary/split-c-sharp)

## Related

- [String Interpolation](https://www.ask-codey.com/lessons/strings-in-csharp-string-interpolation)
- [Useful String Methods](https://www.ask-codey.com/lessons/strings-in-csharp-useful-string-methods)
- [Common String Tasks](https://www.ask-codey.com/lessons/strings-in-csharp-common-tasks)

Source: https://www.ask-codey.com/lessons/exercise-strings