MVC5 如何使用异步来执行渐进式任务？

Question

I have a need. I have an MVC5 website. i am using normal contorller-model structure. Where I execute a controller function from Javascript. I have to process some xml files as they are uploaded. What happens when the controller executes the function for the first time it doesnt come back to the browser until all the xml files are processed.

So here is what i want. I want to execute controller function to execute model method. In that method i want pick all xml files and then i want asynchronously process them. here is the code:

var raw = new DirectoryInfo(xconfig.Directory.FullName + "//raw");
if (raw.Exists)
{
    var xmls = raw.GetFiles("*.xml");
    foreach (var xml in xmls)
    {
        if(ProcessedXmlFiles != null)
        {
            if(!ProcessedXmlFiles.Contains(xml.Name))
            {

                ExportData(xml);
                ProcessedXmlFiles.Add(xml.Name);
            }
        }
    }
}

When the above code is executing, I call another javascript method to get the updates how many files have been processed using normal ajax call. So I just call another contrller method where I return the ProcessedXmlFiles.Count to know how many of them have been processed so far!

Answer 1

You can simply make your action return a Task and place your process inside a Task.Run .

public async Task<ActionResult> MyAction(object param)
{
    var raw = new DirectoryInfo(xconfig.Directory.FullName + "//raw");
    if (raw.Exists)
    {
        await Task.Run(() => 
        {
            var xmls = raw.GetFiles("*.xml");
            foreach (var xml in xmls)
            {
                if(ProcessedXmlFiles != null)
                {
                    if(!ProcessedXmlFiles.Contains(xml.Name))
                    {
                        ExportData(xml);
                        ProcessedXmlFiles.Add(xml.Name);
                    }
                }
            }
        });
        // Do something
    }

    return View();
}

EDIT: Since OP seems to be expecting a different behavior than what asynchronous programming can offer, I suggest using a background worker instead but take note that using background workers in web apps is not desirable. ASP.NET works in a request-response manner. I suggest letting the user wait for the process to end before rendering the view.

public ActionResult MyAction(object param)
{
    ExecuteBackgroundWorker(param); // your model containing the method you want to execute
    return View(); // This will return the view while the background worker proceeds.
}

public void ExecuteBackgroundWorker(object param)
{
    BackgroundWorker bgWorker = new BackgroundWorker();
    bgWorker.DoWork += bgWorker_DoWork;
    bgWorker.RunWorkerCompleted += bgWorker_RunWorkerCompleted;
    bgWorker.RunWorkerAsync(param);
}

void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // Do Something when work ends
}

void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
    var OPsModel = (MyModel)e.Argument; // Cast object back to original model
    OPsModel.ExecuteProcess(); // Execute the process
}