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在阅读了ASP.NET MVC 2 中关于 AsyncControllers 的文档后，我想知道在这种情况下实现 ajax 进度条的最佳方法是什么。本教程根本没有涵盖这一点，这似乎有点奇怪。

我猜想实现 AJAX 进度条需要额外的操作方法来返回当前任务的状态。但是，我不确定在工作线程和该操作方法之间交换有关任务状态的信息的最佳方式。

到目前为止，我最好的想法是将有关当前进度的信息与唯一 ID 一起放入 Session 字典中，并与客户端共享该 ID，以便它可以轮询状态。但也许有一种我没有注意到的更简单的方法。

最好的方法是什么？

谢谢，

阿德里安

4

1 回答 1

16

Very interesting question! Actually it seems that it is not a task for AsyncController. Async controllers are designed for long-running single-HTTP-query operations at server-side. When you are using async action, this could only help you to release ASP.Net worker thread during some long-running operation(s) and allow it to serve other requests while operation is performed. But from client-side point of view it doesn't matter, is this async controller or not. For client this is just single HTTP request.

You need to redesign this using some long-running queries service in your application. Here is example of controller, that could serve such workflow:

public class LongOperationsController : Controller
{
    public ActionResult StartOperation(OperationData data)
    { 
        Guid operationId = Guid.NewGuid(); // unique identifier for your operation
        OperationsService.DoStartOperation(operationId, data); // service starts to perform operation using separate thread
        return new JsonResult(operationId); // operation id should be sent to client to allow progress monitoring
    }

    public ActionResult GetOperationStatus(Guid operationId) 
    {
        var status = OperationsService.GetStatus(operationId); // this method returns some object, that describes status of operation (e.g. progress, current task etc.)
        return new JsonResult(status); // returning it to client
    }

    public ActionResult GetOperationResult(Guid operationId)
    {
        var result = OperationsService.GetOperationResult(operationId); // this should throw exception if operation is not yet completed
        return new JsonResult(result);
    }

    public ActionResult ClearOperation(Guid operationId)
    {
        OperationsService.ClearOperationResult(operationId); // we should delete operation result if it was handled by client
        return true;
    }
}

And here are client-side code, that could interact with this controller:

var operationId;
function startOperation(data) {
    $.post('/LongOperations/StartOperation', data, function(response) {
        operationId = response; // store operationId
        startOperationMonitoring(); // start
    }, 'json');
}

function startOperationMonitoring() {
    // todo : periodically call updateOperationStatus() to check status at server-side
}

function updateOperationStatus() {
    // todo : get result of GetOperationStatus action from controller 
    // todo : if status is 'running', update progress bar with value from server, if 'completed' - stop operation monitoring and call finishOperation()
}

function finishOperation() {
    // todo : get result of GetOperationResult action from controller and update UI
    // todo : call ClearOperation action from controller to free resources
}

This is very basic concept, there are some missed items here, but I hope you will get the main idea. Also it's up to you how to design components of this system, for example:

  • use singleton for OperationsService, or not;
  • where and how long operation result should be stored (DB? Cache? Session?);
  • is it really required to manually release resources and what to do when client stopped to monitor operation (user closed browser) etc.

Best luck!

于 2011-01-18T22:24:32.673 回答