c# - What's the best way to Run a Task that is returned by a Method? - Stack Overflow

admin管理员组

文章数量:1333693

Trying to run a Task returned by a Method and get the Result,

How do you run the returned Task and get the result?

using System;
using System.Threading.Tasks;
                    
public class Program
{
    public static void Main()
    {
        var a = Test.DoWork();
    }
}

public class Test
{
    public static Task<string> DoWork()
    {
        var a = new Task<string>(() =>
        {
              return "Test Message";
        });

        return a;
    }   
}

Run a Task

Trying to run a Task returned by a Method and get the Result,

How do you run the returned Task and get the result?

using System;
using System.Threading.Tasks;
                    
public class Program
{
    public static void Main()
    {
        var a = Test.DoWork();
    }
}

public class Test
{
    public static Task<string> DoWork()
    {
        var a = new Task<string>(() =>
        {
              return "Test Message";
        });

        return a;
    }   
}

Run a Task

• c#
• task
• task-parallel-library

Share Improve this question Follow edited Jan 3 at 22:00 Progman 19.6k77 gold badges5555 silver badges8282 bronze badges asked Nov 20, 2024 at 12:39 user28395223user28395223 7

• 6 Don't use the Task constructors. – Johnathan Barclay Commented Nov 20, 2024 at 12:40
• 1 Change public static void Main() to public static async Task Main(). You can then use await Test.DoWork() to get the result. – Klaus Gütter Commented Nov 20, 2024 at 12:45
• 1 @KlausGütter Not so for the OP's example, because the Task has not been scheduled. – Johnathan Barclay Commented Nov 20, 2024 at 13:03
• You need to either start the task explicitly or use Task.Run to start it automatically. And, of course, as @KlausGütter said, use async and await to handle asynchronous operations. – Anthony Shoshi Gomes Commented Nov 20, 2024 at 13:12
• Just use Task.Run and change void Main() to async Task Main(). The entire question is based on the incorrect assumption that tasks are threads. They aren't, and there's no good reason to create and return "cold" tasks by using the Task constructor. – Panagiotis Kanavos Commented Nov 20, 2024 at 13:52

 |  Show 2 more comments

2 Answers 2

Sorted by: Reset to default 1

Task represents some work that will complete in the future, so asking how to run an already created task makes little sense.

I'm guessing you wanted to do something like:

public class Program
{
    public static async Task Main()
    {
        var a = await Test.DoWork();
    }
}

public class Test
{
    public static Task<string> DoWork()
    {
        return Task.Run(() => "Test Message");
    }   
}

I.e. produce a message on another thread, and await the result in the main method. You can also use .Result instead of async/await to get the result, but this can easily result in deadlocks in an UI application, so async/await is the generally recommended method.

If you need to return a task, but already have the result available you can use Task.FromResult:

return Task.FromResult("Test Message");

If you want to run something several times you can create a delegate from a method:

Func<Task<string>> myDelegate = Test.DoWork; 
var a = await myDelegate();
var b = await myDelegate();

This can be useful to pass factory methods to other methods or classes.

using System;
using System.Threading.Tasks;

public class Program
{
    // Main method should be async to use await directly
    public static async Task Main()
    {
        // Await the result of the task returned by DoWork
        var result = await Test.DoWork();
        
        // Print the result
        Console.WriteLine(result);
    }
}

public class Test
{
    // Method returns a Task<string> and is marked as async
    public static async Task<string> DoWork()
    {
        // Simulate some asynchronous operation (e.g., delay)
        await Task.Delay(1000); // Simulating delay (like I/O operation)

        // Return the result asynchronously
        return "Test Message";
    }
}

Main method is asynchronous (async Task Main()), which is the modern C# way to run asynchronous code in console applications.

The DoWork method is asynchronous (async Task DoWork()), and it uses await Task.Delay(1000) to simulate some asynchronous operation (such as I/O or a web request). It returns a string after the simulated delay.

本文标签： cWhat39s the best way to Run a Task that is returned by a MethodStack Overflow