Difference between Thread, Task and async / await topics

Let's try to break down each question:

so if we create a new thread with class Thread, do we use the thread from ThreadPool or create a new one?

ThreadPool

does what its name indicates, it's a thread pool. When you use a class Thread

, you create a new thread that is not related to those that exist in ThreadPool

.

In msdn we can read: "Represents an asynchronous operation". but creating a new thread and using asynchronous are two different ways, right?

Right. Performing an asynchronous operation does not mean "create a new thread and work on that thread". I mean I am doing things in parallel. Asynchronous operations usually do not require any additional threads in the process, they are naturally asynchronous right down to the OS itself.

So if we are using a task library, are we creating asynchronous operations or are we creating a new thread?

You can do both:

1. Promise-style tasks - they are well represented by async-await
   
   operators async-await
   
   in C # 5. They are asynchronous operations that do not require the use of threads. An example of this can be found in various BCL classes such as classes Stream
   
   , HttpClient
   
   etc. Note that most of the HttpClient
   
   / inference- related classes use a promise style task.

2. Using Task.Run
   
   or Task.Factory.StartNew
   
   . This will take the thread ThreadPool
   
   and execute the provided delegate internally, unless you explicitly tell it you want to create a new one TaskCreationOptions.LongRunning
   
   with TaskCreationOptions.LongRunning
   
   .

If so, when should we use the async / await keywords?

async-await

consistent with everything that is awaitable

. awaitable

is any class / structure that has a method GetAwaiter

that returns a type that implements an interface INotifyCompletion

or ICriticalNotifyCompletion

. You can read more about async-await

here