I have a solution - :)
made a JS, that executes on window load, gets the screen hight and width of the monitor, sends the data to a Webhandler (.ashx), via ajax as json datatype, the Webhandler stores the values in HttpContext.Session variables and can be retrieved were it is needed (e.g. in a .cshtml, or .aspx).
made a JS, that executes on window load, gets the screen hight and width of the monitor, sends the data to a Webhandler (.ashx), via ajax as json datatype, the Webhandler stores the values in HttpContext.Session variables and can be retrieved were it is needed (e.g. in a .cshtml, or .aspx).