Completing tasks

C# course · Beginner · Lesson 86/116

Learn to update task status with CompleteTask.

Completing tasks

To mark a task as done we will write the CompleteTask method. This method sets the IsDone field of the task at a given index to true.

The method signature: static void CompleteTask(List<Task> tasks, int index). The body is a single line: tasks[index].IsDone = true;. Here tasks[index] gives the task, .IsDone gives its status field.

Access by index

The list is accessed with the indexer tasks[i]; the first task is tasks[0], the second tasks[1]. Indices start at 0 and go up to tasks.Count - 1.

To update a task's field you first access it then assign: tasks[0].IsDone = true;. The syntax is similar to modifying an array element; you only add a dot to select a field.

Exercise CompleteTask method

Write the body of CompleteTask: tasks[index].IsDone = true;. In Main, add two tasks, call ListTasks(tasks), then call CompleteTask(tasks, 0) and print tasks[0].IsDone with Console.WriteLine.

Show example solution

Add tasks[index].IsDone = true; to the CompleteTask body, write CompleteTask(tasks, 0); Console.WriteLine(tasks[0].IsDone); in Main.
Example solution:
using System;
using System.Collections.Generic;

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

class Program
{
    static void AddTask(List<Task> tasks, string title)
    {
        tasks.Add(new Task { Title = title, IsDone = false });
    }

    static void ListTasks(List<Task> tasks)
    {
        foreach (Task t in tasks)
        {
            Console.WriteLine(t.Title);
        }
    }

    static void CompleteTask(List<Task> tasks, int index)
    {
        // Mark the task as done
        tasks[index].IsDone = true;
    }

    static void Main()
    {
        List<Task> tasks = new List<Task>();
        AddTask(tasks, "Buy bread");
        AddTask(tasks, "Buy milk");
        ListTasks(tasks);
        // Add a CompleteTask call and print the status
        CompleteTask(tasks, 0);
        Console.WriteLine(tasks[0].IsDone);
    }
}

Test yourself

What is printed after IsDone = true?

List<Task> tasks = new List<Task>();
tasks.Add(new Task { Title = "Buy bread", IsDone = false });
tasks[0].IsDone = true;
Console.WriteLine(tasks[0].IsDone);

false
0
Buy bread
True

Show answer

True — Correct. After IsDone = true, Console.WriteLine prints True.

Update status

tasks[____].IsDone = true;
Console.WriteLine(tasks[0].IsDone);

Show answer

tasks[0].IsDone = true;
Console.WriteLine(tasks[0].IsDone);

Match each expression to its meaning

tasks[0]

First task
tasks[i]

i-th task
.IsDone = true

Mark done
tasks.Count

Task count

Completing tasks