How to read page url/query parameter?

Every Radzen Blazor application with Security enabled has the following code:

var query = System.Web.HttpUtility.ParseQueryString(new Uri(UriHelper.ToAbsoluteUri(UriHelper.Uri).ToString()).Query);

var error = query.Get("error");

redirectUrl = query.Get("redirectUrl");;

That's how to work with query string parameters. Those are all Execute C# actions.

Can you point me to such questions so I can link my reply in this thread?