var pollUploadStatus = function( dlg )
    {            
      var iframe = dlg.find( "IFRAME.target" ).get( 0 );
      
      var finallize = function( msg, error, result )
      {
        dlg.each( function() 
        { 
          var self = this;          
          self.unblock(); 
          self.displayMessage( { message : msg,          
                                 title : error ? "Ошибка" : "Сообщение",
                                 onclose : function()
                                 {
                                   if ( !error ) {
                                     dlg.find( "FORM" ).attr( "target", "" );
                                     dlg.find( "IFRAME.target" ).remove();
                                     closeDialog( dlg );                                     
                                     self.dialogOptions.onSuccess( result );                                     
                                   }
                                 }
                               } );
        } );        
      }
      var uploadSucceeded = function( data )
      {               
        finallize( dlg.get( 0 ).dialogOptions.successMessage, false, data );        
      }
      var uploadFailed = function( msg )
      {        
        finallize( dlg.get( 0 ).dialogOptions.failureMessage + msg, true );
      }                 

      var timeout = g_UploadTimeout;
      var enqueuePoll = function()
      {
        setTimeout( poll, g_PollInterval );
      }
      var poll = function()
      {
        // Check timeout
        timeout -= g_PollInterval;
        if ( timeout <= 0 ) {
          uploadFailed( "время ожидания окончания операции истекло" );
          return;
        }
        // Retrieve JSON content
        var json = undefined;
        try {
          json = $( iframe.contentWindow.document ).find( "BODY > PRE" ).html();
        } catch ( e ) {
          json = undefined;
        }
        if ( json == undefined || ( typeof( json ) == "string" && json.length == 0 ) ) {
          enqueuePoll();
          return;
        }    
        // Convert JSON to object
        var result;
        try {          
          eval( "result = " + json );
        } catch ( e ) {
          result = undefined;
        }
        if ( result == undefined || result.Success == undefined ) {
          uploadFailed( "неожиданный ответ от сервера" );
          return; 
        }
        // Check result
        if ( result.Success == true ) {          
          uploadSucceeded( result.Data );                    
        } else {
          var msg = "";
          var messages = result.ErrorMessages;
          if ( messages != undefined && messages.length != undefined && messages.length > 0 ) {
            if ( messages.length == 1 )
              msg = messages[0];
            else {
              for( var i = 0; i < messages.length; i++ )
                msg += "<li>" + messages[i] + "</li>";
              msg = "<ul>" + msg + "</ul>";
            }
          }          
          uploadFailed( msg );
        }
      }
      enqueuePoll();
    }