HttpContext Context = HttpContext.Current;
value = "http://localhost" + Context.Request.RawUrl;

// Gets the base url in the following format:
// "http(s)://domain(:port)/AppPath"
HttpContext.Current.Request.Url.Scheme
    + "://"
    + HttpContext.Current.Request.Url.Authority
    + HttpContext.Current.Request.ApplicationPath;

var baseUri = new Uri(HttpContext.Current.Request.Url, "/");

string loginUrl = Request.Url.GetLeftPart(UriPartial.Authority) + VirtualPathUtility.ToAbsolute("~/") + "Login/Login.aspx?UserName=" + LoggedinUser["UserName"] + "&Password=" + LoggedinUser["Password"];