Add parameters to the chilkat link address

Actually, I send a post request via the link https://mysite.com/login?preferredLanguageCode=EN but the link is clipped and the request is received goes to https://mysite.com/login without parameters:

req.AddParam("username", Login); req.AddParam("password", Password); string post = http.PostUrlEncoded("https://mysite.com/login?preferredLanguageCode=EN", req).BodyStr;