Is it possible to pass the value of a Javascript variable to a C#variable?

Question

The idea is to use javascript to detect the screen resolution, and take the value of the variable of this javascript and pass to the variable of C#. The only thing that’s crossed my mind is creating an input to manipulate the variables, but I believe you have another method. In practice the idea would be more or less this:

   <script type="text/javascript">
        var varJavascrpt = $(window).width();
    </script>
    @{
        var varCSharp = varJavascript;
    }

Answer 1

To pass Javascript values to Asp.net, a new request (e.g. using AJAX) is required. It is not possible to check the resolution before making the request because JS in this case is client-side, while Asp.net is server-side, which means that the JS code will only run in the browser after the request that downloaded the page is completed. The server does not have access to JS-independent code running in the browser, unless you inform it directly by making a new request.

But this approach is bad, because the decision whether or not to display a component in the navbar will be dependent on a second request after loading the page. The ideal is to do this with client-side technologies so you don’t have to go to the server and then come back, saving resources, accelerating page loading and not depending on JS enabled in the browser.

It is possible to do this with JS, but CSS3 introduced the media query, starting the movement of responsive layouts that automatically adjust according to the resolution (and the server is agnostic about it). For example, to hide a navbar when the resolution is less than or equal to 600px, do so:

@media (max-width: 600px) 
{
  .navbar {
    display: none;
  }
}