CSharp Async Tasks TaskRun

C# Async: Tasks, Task.Run, and Task.Delay

This lesson builds on the basics from CSharp-AsyncAwait-Basics.md and focuses on:

• Task as the core representation of an asynchronous operation
• Task.Run for running CPU-bound work on a thread pool thread
• Task.Delay for non-blocking delays

Related wiki pages:

• Async basics: CSharp-AsyncAwait-Basics.md (renamed from Lesson03.12.2025.md)
• General C# topics: CSharpBible.md
• Libraries and tasks: CSharpBible-Libraries.md
• MVVM and async commands: CSharpBible-MVVM-Standard.md, CommunityToolkit.MVVM.md

Official documentation:

• Tasks and async: https://learn.microsoft.com/dotnet/standard/parallel-programming/task-based-asynchronous-programming

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1. Task and async/await

• Task represents an ongoing operation that may complete in the future.
• Task<T> represents an operation that produces a result of type T.
• async/await is syntax sugar that lets you write asynchronous code in a sequential style.

You typically do not manage custom "events" to make methods awaitable – the compiler generates a state machine from your async method.

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2. Example: running work with Task.Run

Use Task.Run for CPU-bound work that should not block the current thread (e.g., the UI thread). For I/O-bound work you usually call naturally async APIs directly, without Task.Run.

using System;
using System.Threading.Tasks;

namespace CSharpAsync
{
    class Program
    {
        static async Task Main(string[] args)
        {
            Console.WriteLine("Starting...");

            try
            {
                string message = "Hello, world!";

                // Run CPU-bound work on a thread pool thread
                await Task.Run(async () =>
                {
                    Console.WriteLine(message);

                    // Non-blocking delay to simulate work
                    await Task.Delay(100); 
                });
            }
            catch (Exception ex)
            {
                Console.WriteLine($"An error occurred: {ex}");
            }

            Console.WriteLine("Finished. Press any key to exit...");
            Console.ReadKey();
        }
    }
}

Notes:

• Task.Run schedules the delegate on the thread pool.
• await Task.Run(...) asynchronously waits for completion.
• Task.Delay(100) is preferred over Thread.Sleep(100) in async code because it does not block the thread.
• Removed the invalid Console.DisableEndOfProcess() – there is no such API in System.Console.

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3. When to use Task.Run

Use Task.Run mainly when:

• You have CPU-bound work that must not run on the UI thread.
• You are in a console or desktop app and want to keep the UI responsive.

Do not wrap already-async I/O calls (like HttpClient.GetAsync) in Task.Run; just await them directly (see CSharp-AsyncAwait-Basics.md).

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4. Next steps

• Explore exception handling in async code together with CSharp-Exceptions-TryCatch.md.
• Use tasks and async methods in MVVM commands (CommunityToolkit.MVVM.md).
• Read the official task-based async programming guide linked above for advanced patterns (cancellation, progress, etc.).