Asynchronous parallel tasks not working

Question

0.00/5 (No votes)

See more:

, +

So I have this command :

C#

public DelegateCommand GenerateReportForAllClientsCommand { get; set; }
public bool CanExecuteGenerateReportForAllClients()
{
    return true;
}
public async void GenerateReportForAllClientsExecute()
{
    if (ClientList.Count < 1)
        return;
    
    IsGenerating = true;
    
    await Task.WhenAll(clientList.Select(i => ReportManager.GeneratePdfReportAsync(i.Client)));
    
    IsGenerating = false;
}

and this method :

C#

public static async Task GeneratePdfReportAsync(ClientInfoModel client)
{
    // Generates a pdf report of the client...
}

The problem is that when I call the command my application freezes, which I don't want it to do... This doesn't happen when I do a single report like so in this other command:

C#

public async void GenerateReportExecute()
{
    IsGenerating = true;
    
    await ReportManager.GeneratePdfReportAsync(SelectedClient);
    
    IsGenerating = false;
}

The method above works perfectly as expected, while generating the file, the application is still available. Does anyone know why async doesn't work anymore when I use Task.WhenAll ?

Posted 7-Aug-14 2:25am

Yannick Brodard

Updated 7-Aug-14 2:27am

v2

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Yannick Brodard · Accepted Answer · 2014-08-07T20:05:00

By searching the web, I found a convenient answer to my problem.

I had an other async / await in my GeneratePdfReportAsync method, and I've discovered that a Task or Task<T> object need the UI Thread to be available. But in this case for this method, I didn't need the UI Thread, but it was still accessing it to verify the result of my task and so blocking my UI until all my tasks were finished.

The solution was that during the await from other method in the GeneratePdfReportAsync method, I've added ConfigureAwait(false) witch tells the Task not to call the UI.

C#

messages = await ClientInfoManager.GetMessagesFromClientAsync(client, true).ConfigureAwait(false);

I've found the solution to my problem thanks to a very helpful tutorial for asynchronous and parallel programming on C#.

Links :
Part 1
Part 2