Ajax.BeginForm ActionResult Task Delay Goto?

I need to delay the ActionResult return Content until all the Tasks are completed. I like the way the Ajax.BeginForm uses the LoadingElementId to start the spinner.gif. The problem is the ActionResult returns before the Tasks are complete, so the spinner is useless.

[View]
   @using (Ajax.BeginForm("Import", "Books", new AjaxOptions { HttpMethod = "Post", UpdateTargetId = "result", LoadingElementId = "loading"}))
{
   ...
}

<div id="loading">
       <img src="~/Content/Images/spinner.gif" height="30" />
</div>

[Action]
    public async Task<ActionResult> Import(ImportViewModel model)
    {
           bool books = false; 

           foreach(....)
           {
                  books = await ImportBooks();
            }

           wait:

                Task.Delay(5000).Wait();

                if (books == false)
                {
                    goto wait;
                }
                else                    
                    return Content("Books import completed!");            
     }

     public async Task<bool> ImportBooks()
     {
          ....
          await context.SaveChangesAsync();

         return true;
     }

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