Task model

Design the Task class and its properties.

Project: To-do list

In this 5-lesson project you will build a to-do list application. Each lesson adds one piece; the final lesson gives you a complete command-line application.

The first lesson designs the Task class. A task will have two fields: Title (the title text) and IsDone (whether it is done). This class is used in every lesson of the project, so a solid design matters.

Class and fields

A class groups related data under a single type. It is declared with class Task { ... }. Variables inside a class are called fields; the public keyword allows access from outside.

A new instance of the class is created with new Task(). Fields are accessed with the dot: t.Title. This is similar to the .Length property of arrays.

Exercise Task class and instance

Define the Task class with the fields public string Title; and public bool IsDone;. In Main, create a task with new Task(), assign "Buy bread" to Title and print Title with Console.WriteLine.

Show example solution

Add public string Title; and public bool IsDone; inside Task. In Main write Task t = new Task(); t.Title = "Buy bread"; Console.WriteLine(t.Title);.
Example solution:
using System;

class Task
{
    // Declare the Title and IsDone fields
    public string Title;
    public bool IsDone;
}

class Program
{
    static void Main()
    {
        // Create a Task, set its title and print
        Task t = new Task();
        t.Title = "Buy bread";
        Console.WriteLine(t.Title);
    }
}

Test yourself

What does the Task instance's Title print?
```
class Task
{
    public string Title;
    public bool IsDone;
}
Task t = new Task();
t.Title = "Buy bread";
Console.WriteLine(t.Title);
```
- Buy bread
- null
- Task
- Empty
Show answer

Buy bread — Correct. After t.Title = "Buy bread", Console.WriteLine prints Buy bread.

Declare a class field

class Task
{
    public string Title;
    public ____
}

Show answer

class Task
{
    public string Title;
    public bool IsDone;
}

Match each expression to its meaning

public string Title

Text field
public bool IsDone

Boolean field
new Task()

New instance
t.Title

Field access

Next lesson: Adding tasks

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