MVC BeginForm with querystring

For a provider hosted app in SharePoint any request to the server must preserve standard SharePoint tockens in query string. I have found a blog that explains how to achieve similar functionality in plain MVC
https://www.danylkoweb.com/Blog/quick-tip-querystrings-with-aspnet-mvc-beginform-FO

In practise, instead of adding another BeginFormQueryString extension to Html object I only copied the extension method on query string

public static RouteValueDictionary ToRouteValueDictionary(this NameValueCollection collection)

        {

            var routeValues = new RouteValueDictionary();

            foreach (string key in collection)

            {

                routeValues[key] = collection[key];

            }

            return routeValues;

        }

And then added the routevalues to OOB BeginForm method like so:

@using (@Html.BeginForm("myAction", "myController", Request.QueryString.ToRouteValueDictionary(), FormMethod.Post))

{