The Task class
Learn the asynchronous operation represented by Task.
The Task class
The Task class represents background work in C#. Use Task for operations that return no result, and Task<T> for ones that do. A Task may be running, completed, or faulted.
To produce an already-completed Task, write Task.FromResult(42); this gives a result with no real waiting. For an empty Task use Task.CompletedTask. These are useful in tests and deterministic flows.
Using Task<T>
To get the result of a Task<T> you use await: int n = await t;. When t completes, its Result property holds the value; await unwraps it safely.
Writing t.Result directly causes a synchronous wait that can deadlock. So always read the result through await. If the task faulted, await rethrows the exception.
Exercise Return a value with Task.FromResult
Define a static Task<int> GetAge() method. In its body return Task.FromResult(30). Make Main a static async Task Main; read the result with int age = await GetAge(); and print it with Console.WriteLine(age);.
Show example solution
In the body write return Task.FromResult(30);. In Main write int age = await GetAge(); Console.WriteLine(age);
Example solution:
using System;
using System.Threading.Tasks;
class Program
{
static Task<int> GetAge()
{
return Task.FromResult(30);
}
static async Task Main()
{
int age = await GetAge();
Console.WriteLine(age);
}
}Test yourself
-
Create a Task<int>
Task<int> t = Task.____(42);Show answer
Task<int> t = Task.FromResult(42); -
Match each Task member to its role
- Task.CompletedTask
- Empty, completed Task
- Task.FromResult(42)
- Ready result Task
- Task.Run(...)
- Sends work to the pool
- Task.Delay(100)
- Waits on a timer
-
What does Task.CompletedTask represent?
- A running Task
- A cancelled Task
- A faulted Task
- An already completed empty Task
Show answer
An already completed empty Task — Correct. Task.CompletedTask is a completed empty Task.