CODEWITHSUNDEEP
asp.netasp.net-mvc-3asp.net-4.0
Tom
Tom

Reputation: 12659

'System.Threading.Tasks.Task' does not contain a definition for 'Result'

I have a facebook query which is as follows

var client = new FacebookClient(accessToken);
var dynamic = client.Get(connection, new { fields = "name,from,story,message,picture,comments", limit = count});
foreach (var dynPost in results.data)
{
     posts.Add(ConvertToPost(dynPost));
}

I am trying to make this quicker by making lots of smaller requests to Facebook in parallel.

using (profilingService.Start("Facebook calls"))
{ 
    var pullSize = 25;
    var numberOfCalls = (int)Math.Ceiling(count / (double)pullSize);

    var taskQueue = new Queue<Task>();
    for (int i = 0; i < numberOfCalls; i++)
    {
        taskQueue.Enqueue(Task.Factory.StartNew(() =>
        {
            var offset = i * pullSize;
            var client = new FacebookClient(accessToken);
            return client.Get(connection, new { fields = "name,from,story,message,picture,comments", limit = 25, offset = offset });
        }));
    }

    Task.Factory.ContinueWhenAll(
        taskQueue,
        tasks =>
        {
            //t.Result here is giving me the error
            var results = tasks.Select(t => t.Result);
            foreach (var result in results)
            {
                foreach (var dynPost in result.data)
                {
                    posts.Add(ConvertToPost(dynPost.data));
                }
            }
        });
}

First of all I am getting an error on var results = tasks.Select(t => t.Result);

Error 361 'System.Threading.Tasks.Task' does not contain a definition for 'Result' and no extension method 'Result' accepting a first argument of type 'System.Threading.Tasks.Task' could be found (are you missing a using directive or an assembly reference?)

t is of type Task<AntecedentResult>

Which led me to this page, but have still not able to resolve it. What's wrong with this async Task method?

Also, I haven't had much experience with this sort of parallel coding, anything I am doing wrong or should be doing in a different way?

Upvotes: 2

Views: 8935

Answers (1)

Ed Chapel
Ed Chapel

Reputation: 6932

The problem is the Queue<Task>. Task alone does not have a Result property. However, Task<Foo> has a Result property of type Foo. (I don't know what client.Get(...) returns, let's call it Foo for now:

var taskQueue = new Queue<Task<Foo>>();

The ContinueWhenAll method does not support Queue<>, only Task[] and Task<>[], so you need to convert it to an array first.

Task.Factory.ContinueWhenAll(
    taskQueue.ToArray(),
    tasks =>
    {
        var results = tasks.Select(t => t.Result);
        foreach (var result in results)
        {
            ...
        }
    });
}

Upvotes: 6

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