async Task PopulateInputFile(HtmlElement file, String photo)
{
file.Focus();
// delay the execution of SendKey to let the Choose File dialog show up
var sendKeyTask = TaskEx.Delay(500).ContinueWith((_) =>
{
// this gets executed when the dialog is visible
SendKeys.SendWait(photo + "{ENTER}");
}, TaskScheduler.FromCurrentSynchronizationContext());
file.InvokeMember("Click"); // this shows up the dialog
await sendKeyTask;
file.RemoveFocus();
// delay continuation to let the Choose File dialog hide
await TaskEx.Delay(500);
}