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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.

Practice 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.

Starter code

Program.cs
using System;

class Task
{
    // Declare the Title and IsDone fields
}

class Program
{
    static void Main()
    {
        // Create a Task, set its title and print
    }
}

Sample solution

Program.cs
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);
    }
}

Expected output

Buy bread

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What does the Task instance's Title print?

Program.cs
class Task
{
    public string Title;
    public bool IsDone;
}
Task t = new Task();
t.Title = "Buy bread";
Console.WriteLine(t.Title);
  • Buy bread Correct answer
  • null
  • Task
  • Empty

Explanation: After t.Title = "Buy bread", Console.WriteLine prints Buy bread.

2 Declare a class field

Question 
class Task
{
    public string Title;
    public ____
}
Answer 
class Task
{
    public string Title;
    public bool IsDone;
}

Explanation: bool IsDone; declares the boolean field.

3 Match each expression to its meaning

Term Meaning
public string Title Text field
public bool IsDone Boolean field
new Task() New instance
t.Title Field access

All lessons in Beginner

1 C# basics

  1. What is C# and .NET?
  2. Your first program
  3. Console.WriteLine
  4. Comments
  5. Compile and run
  6. Summary - C# basics

2 Variables

  1. Declaring variables
  2. The var keyword
  3. Constants
  4. Type inference
  5. Variable scope
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. Char and bool
  4. String basics
  5. Value and reference types
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Bitwise operators
  6. Summary - Operators

6 String basics

  1. Declaring strings
  2. String interpolation
  3. String concatenation
  4. String.Format
  5. Verbatim strings
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and else if
  3. The switch statement
  4. Pattern matching
  5. The ternary operator
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. The foreach loop
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding products
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Array length
  4. Multidimensional arrays
  5. Jagged arrays
  6. Summary - Arrays

11 Array methods

  1. Array.Sort
  2. Array.Reverse
  3. Array.IndexOf
  4. Array.Copy
  5. Array.Find and FindAll
  6. Summary - Array methods

12 Collections

  1. List<T> basics
  2. List<T> methods
  3. Dictionary<K,V>
  4. Dictionary access
  5. HashSet<T>
  6. Summary - Collections

13 Methods

  1. Defining methods
  2. Return values
  3. void methods
  4. Method overloading
  5. Local functions
  6. Summary - Methods

14 Method parameters

  1. Parameterized methods
  2. Default parameters
  3. The params keyword
  4. ref parameters
  5. out parameters
  6. Summary - Method parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string methods

  1. Substring
  2. IndexOf and LastIndexOf
  3. Split and Join
  4. Trim and Pad
  5. Replace
  6. Summary - Advanced strings

17 Console I/O

  1. Console.ReadLine
  2. Console.ReadKey
  3. int.Parse and TryParse
  4. double.Parse
  5. Console formatting
  6. Summary - Console I/O

18 Enums

  1. Defining enums
  2. Enum values
  3. Enum casting
  4. Enum.Parse
  5. Flags attribute
  6. Summary - Enums

19 Exception basics

  1. try/catch
  2. finally block
  3. throw
  4. The Exception class
  5. Custom exceptions
  6. Summary - Exception basics

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together