Sys.WebForms.PageRequestManager.getInstance().add_beginRequest (BeginRequest);
       Sys.WebForms.PageRequestManager.getInstance().add_endRequest (EndRequest);
       
       function BeginRequest(sender, args){
         var arr=document.getElementsByTagName("select");
         for(i=0;i<arr.length;i++){
               arr[i].style.visibility="hidden";
         }
         ResizeLoading();
         window.onscroll=ResizeLoading;
         window.onresize=ResizeLoading;
         
       }
       function EndRequest(sender, args){
          window.onscroll=null;
          window.onresize=null;
          var mask= $get("LoadingMask");
          if(mask!=null)
          {
            mask.style.height=0;
            mask.style.visibility="hidden";
          }
          var arr=document.getElementsByTagName("select");
          for(i=0;i<arr.length;i++){
               arr[i].style.visibility="visible";
          }
       }
       
       function ResizeLoading(){
           var mask= $get("LoadingMask");
           var loading=$get("shadow-container");
           if(mask!=null && loading!=null)
           { 
               mask.style.height=(document.documentElement.offsetHeight>document.body.clientHeight?document.documentElement.offsetHeight:document.body.clientHeight)+50;
               mask.style.width=document.documentElement.offsetWidth>document.body.clientWidth?document.documentElement.offsetWidth:document.body.clientWidth;
               mask.style.visibility="visible";
               
               var divHeight   =  parseInt(loading.offsetHeight,10)   
               var divWidth   =   parseInt(loading.offsetWidth,10)   
               var docWidth   =   document.documentElement.offsetWidth;   
               var docHeight   =  document.documentElement.offsetHeight;   
               loading.style.top   =   (docHeight-divHeight)/2+parseInt(document.documentElement.scrollTop,10) ;
            }
       }