programatically show/display loading using c#

hello ,

   I am trying to show/hide loading panel programatically using modalpopup.show() and

modalpopup.hide() but modalpopup.hide() is not working. Can anyone tell me how can i start and stop loading/processing in case where data is being fetched asynchronously from multiple API and as soon as the first data is available stop the loading sign.

 

thax

Avishek