Using SPLongOperation Within ItemUpdating Event Receiver

Question

I have an event receiver triggered on ItemUpdating that may take some time to run. The code is as follows:

using (SPLongOperation longOperation = new SPLongOperation())
{
    //Custom Messages on the Spinning Wheel Screen
    longOperation.LeadingHTML = "Enumerating ...";
    longOperation.TrailingHTML = "Please wait while the related items are checked.";

    //Start the long operation
    longOperation.Begin();

    foreach (SPListItem someItem in items)
    {

        strNCStatus = ncItem["Status"].ToString();

        if (strStatus != "Closed")
        {
            properties.ErrorMessage = "The Status Of The Item Cannot Be Changed To Closed Because There Are Open Related Items.";
            properties.Status = SPEventReceiverStatus.CancelWithError;
            properties.Cancel = true;
        }
    }

    //End the long operation
    string redirectURL = SPContext.Current.Web.Url;
    longOperation.End(redirectURL);
}

You will notice from the code that SPLongOperation(this.Page) is not calling the this.Page part.

I want the processing page to display while this operation takes place in the ItemUpdating.

I don't have a reference to this.Page because my code is running on ItemUpdating event receiver.

Is it valid to use SPLongOperation within ItemUpdating and if so how can I use SPLongOperation without using this.Page as the parameter?

Answer 1

Event Receivers are Asynchronous and they are getting executed in a separate thread.

To make your requirement work, the first thing you need to do it make the event Synchronous. For that you can use the Sysnchronization property of the Receiver Definition

 ReceiverDefinition.Synchronization=SPEventReceiverSynchronization.Synchronous;

Now the ItemUpdating will get executed by the same UI thread.

Next issue is how to get the HTTPContext object. Solution is to get if from the constructor

SPContext spContext;
HttpContext httpContext;

public ReceiverClass () {
    spContext = SPContext.Current;
    httpContext = HttpContext.Current;
}

public override void ItemUpdating(SPItemEventProperties properties) {
    base.ItemUpdating(properties);
    httpContext.Response.Redirect(spContext.Web.ServerRelativeUrl + "/_layouts/longoperationpage.aspx");
}

Now in longoperationpage.aspx you should do

using (var longRunning = new SPLongOperation(Page))
{
   longRunning.Begin();
   // do your long running operation here 
   longRunning.End(null, SPRedirectFlags.Default, Context, null, "window.frameElement.commonModalDialogClose(1, null);");
}

Answer 2

Basically, you can't do that as SP Context is not available in Event Receivers and vice versa. The SPLongOperation wouldn't know when the event receiver has finished it's work.