How can I determine browser window size on server side C#

Here's an Ajax, asxh handler and session variables approach:

Handler:

using System;
using System.Web;

public class windowSize : IHttpHandler , System.Web.SessionState.IRequiresSessionState  {

    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "application/json";

        var json = new System.Web.Script.Serialization.JavaScriptSerializer();
        var output = json.Serialize(new { isFirst = context.Session["BrowserWidth"] == null });
        context.Response.Write(output);

        context.Session["BrowserWidth"] =  context.Request.QueryString["Width"]; 
        context.Session["BrowserHeight"] = context.Request.QueryString["Height"];
    }

    public bool IsReusable
    {
        get { throw new NotImplementedException(); }
    }
}

Javascript:

window.onresize = function (event) {
    SetWidthHeight();
}
function SetWidthHeight() {
    var height = $(window).height();
    var width = $(window).width();
    $.ajax({
        url: "windowSize.ashx",
        data: {
            'Height': height,
            'Width': width
        },
        contentType: "application/json; charset=utf-8",
        dataType: "json"
    }).done(function (data) {     
        if (data.isFirst) {
            window.location.reload();
        };
    }).fail(function (xhr) {
        alert("Problem to retrieve browser size.");
    });

}
$(function () {
    SetWidthHeight();
});

On aspx file:

...
<script src="Scripts/jquery-1.9.1.min.js"></script>
<script src="Scripts/BrowserWindowSize.js"></script>
...
<asp:Label ID="lblDim" runat="server" Text=""></asp:Label>
...

Code behind:

protected void Page_Load(object sender, EventArgs e)
  {
      if (Session["BrowserWidth"] != null)
      {
          // Do all code here to avoid double execution first time
          // ....
          lblDim.Text = "Width: " + Session["BrowserWidth"] + " Height: " + Session["BrowserHeight"];
      }
  }

Source: https://techbrij.com/browser-height-width-server-responsive-design-asp-net

Here how I solved it using Cookies:

First of all, inside the website main script:

var browserWindowSize = getCookie("_browserWindowSize");
var newSize = $(window).width() + "," + $(window).height();
var reloadForCookieRefresh = false;

if (browserWindowSize == undefined || browserWindowSize == null || newSize != browserWindowSize) {
    setCookie("_browserWindowSize", newSize, 30);
    reloadForCookieRefresh = true;
}

if (reloadForCookieRefresh)
    window.location.reload();

function setCookie(name, value, days) {
    var expires = "";
    if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
        expires = "; expires=" + date.toUTCString();
    }
    document.cookie = name + "=" + (value || "") + expires + "; path=/";
}

function getCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for (var i = 0; i < ca.length; i++) {
        var c = ca[i];
        while (c.charAt(0) == ' ') c = c.substring(1, c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
    }
    return null;
}

And inside MVC action filter:

public class SetCurrentRequestDataFilter : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // currentRequestService is registered per web request using IoC
        var currentRequestService = iocResolver.Resolve<ICurrentRequestService>();

        if (filterContext.HttpContext.Request.Cookies.AllKeys.Contains("_browserWindowSize"))
        {
            var browserWindowSize = filterContext.HttpContext.Request.Cookies.Get("_browserWindowSize").Value.Split(',');
            currentRequestService.browserWindowWidth = int.Parse(browserWindowSize[0]);
            currentRequestService.browserWindowHeight = int.Parse(browserWindowSize[1]);
        }

    }
}