How to add attribute/parameters to the url in ASP.NET Core Razor Pages dynamically?

If the user change or enter the url manually ,I want to add attribute "culture" to the url .

For example the user wants to go to the "post" page and change the url to the "https://localhost:4432/post" manually,then I want to add attribute "?culture=" to the url,I write this code in "post.cshtml.cs" class but it doesn't work :

public IActionResult OnGet()
{
    string culture = "fa";

    if (Request.Cookies.ContainsKey("_culture"))
        culture = Request.Cookies["_culture"].ToString();

    Response.Redirect("/post?culture=" + culture);

    return Page();
}

The result is here:

> This page isn't working:
> localhost redirected you too many times.
> Try clearing your cookies.
> ERR_TOO_MANY_REDIRECTS

You have to break out of the infinite loop of the redirect. If the requested URL does not have the query tag for culture then add it with the redirect and return the page. Else just return the page.

    public IActionResult OnGet()
    {

        string culture = Request.Query["culture"];

        if (String.IsNullOrEmpty(culture))
        {

            culture = "fa";

            if (Request.Cookies.ContainsKey("_culture"))
                culture = Request.Cookies["_culture"].ToString();

            Response.Redirect("/post?culture=" + culture);
        }

        return Page();
    }