Intercettare il metodo httpapplication.endrequest

function showLoading() 
{
  var width = document.body.offsetWidth;
  var height = document.body.offsetHeight;
  var top = 0;
  var left = 0;

  var pnlLoading = document.getElementById('ctl00_ctl00_ContentPage_pnlLoading');
  pnlLoading.style.width = width + 'px';
  pnlLoading.style.height = height + 'px';
  pnlLoading.style.top = top + 'px';
  pnlLoading.style.left = left + 'px';
  pnlLoading.style.visibility = 'visible';
  pnlLoading.style.cursor = 'wait';
  
  var imgLoading = document.getElementById('ctl00_ctl00_ContentPage_imgLoading');
  imgLoading.style.left = ((width - 130) / 2) + 'px';
  imgLoading.style.top = '150px';
  imgLoading.style.visibility = 'visible';
  
  var imgChiudi = document.getElementById('ctl00_ctl00_ContentPage_imgChiudi');
  imgChiudi.style.visibility = 'visible';

  var selects = document.getElementsByTagName('select');
  for (i = 0; i < selects.length; i++)
    selects[i].style.visibility = 'hidden';

  //Serve per ovviare al problema del back e il loading.
  //Se il browser è mozilla... Altrimenti...
  if (document.addEventListener) 
  { 
    //Firefox
    document.addEventListener('DOMContentLoaded', hideLoading, false); 
    document.addEventListener('blur', hideLoading, false); 
  }
  else if (document.attachEvent)
  {
    //Internet Explorer
    var pnlFocus = document.getElementById('ctl00_ctl00_ContentPage_pnlFocus');
    pnlFocus.attachEvent('onload', hideLoading);
    pnlFocus.attachEvent('onblur', hideLoading);

    pnlFocus.style.width = (width - 10) + 'px';
    pnlFocus.style.height = (height - 10)+ 'px';
    pnlFocus.style.top = (top + 10) + 'px';
    pnlFocus.style.left = (left + 10) + 'px';
    pnlFocus.style.visibility = 'visible';
    pnlFocus.style.cursor = 'wait';

    pnlFocus.focus();
  }
  else 
  { 
    document.onload = new Function('hideLoading(e);'); 
    document.onblur = new Function('hideLoading(e);'); 
  }
}
function hideLoading(e) 
{
  var pnlLoading = document.getElementById('ctl00_ctl00_ContentPage_pnlLoading');
  pnlLoading.style.visibility = 'hidden';
  pnlLoading.style.cursor = 'default';

  var imgLoading = document.getElementById('ctl00_ctl00_ContentPage_imgLoading');
  imgLoading.style.visibility = 'hidden';

  var imgChiudi = document.getElementById('ctl00_ctl00_ContentPage_imgChiudi');
  imgChiudi.style.visibility = 'hidden';

  var selects = document.getElementsByTagName('select');
  for (i = 0; i < selects.length; i++)
    selects[i].style.visibility = 'visible';
}