Async code implementation correctness

Question

I have an application where I make a call like this:

myViewModel.ProcessDirectoryAsync(rootDirectoryInfo);

and in myViewModel:

public async ProcessDirectoryAsync(DirectoryInfo rootDirectoryInfo)
{
    await Task.Run(() => ProcessDirectory(rootDirectoryInfo));
}

public void ProcessDirectory(DirectoryInfo rootDirectoryInfo)
{
    // do work and update progress in UI with a bunch of data
}

The idea is that I want my ui to show multiple threads of work, each updating the UI with its progress and data independently.

This code works just fine.

But I wonder if it is not right. If I put an await (as recommended by resharper :) ) on this line:

await myViewModel.ProcessDirectoryAsync(rootDirectoryInfo);

Then I see the threads progress serially, rather than in parallel. Which is not what I want.

So first, is there something inherently evil in the way I've implemented this (which works), and if so what is the correct way?

Have a look at this: Should I expose synchronous wrappers for asynchronous methods?. — Paulo Morgado
– Paulo Morgado, Commented Sep 7, 2014 at 18:32

ths · Accepted Answer · 2014-09-05 23:50:13Z

1

the indirection and async/await seem unneccessary. just call

Task.Run(() => myViewModel.ProcessDirectory(rootDirectoryInfo));

btw., you should always await an async, and async functions should return a Task, except in event handlers. but all of this unneccessary here.

answered Sep 5, 2014 at 23:50

ths

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3 Comments

Nicros Over a year ago

Is there anything dangerous about updating UI components via dependency properties just using Task.Run? That works perfectly as well...

Alexei Levenkov Over a year ago

+1. @Nicros - no, just use normal InvokeRequired/Invoke (or whatever matching methods in framework you are using) as you would do in any other multi-threaded updates of UI elements.

Paulo Morgado Over a year ago

Better yet, do whatever you need to do inside the async part and output the result as the result of the task. Then you await the task and use the result to update the UI.

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