HttpRequest.QueryString 的自動 UrlDecode 問題

HttpRequest.QueryString[“q”] 在用來取得query string的值是很方便, 但是會自動將query string先做過UrlDecode, 這在query string 有某些特殊字元的時候產生問題

直接上Demo

public ActionResult Index()
{
    //sample query string (plain text): q=aaa$bbb+ccc

    //q = "aaa$bbb ccc"
    string q = this.Request.QueryString["q"];


    // solution 1: encode after get query string
    //             useful if query string not contain other characters can be encode
    //q = "aaa%24bbb+ccc" in this case
    string q2 = HttpUtility.UrlEncode(this.Request.QueryString["q"]);

    // solution 2: split string to get value
    //             if query string contain charactors can be encode, this is safety way
    List<string> queryStrings = this.Request.Url.Query.Replace("?", "").Split('&').ToList();
    //q3 = "aaa$bbb+ccc"
    string q3 = queryStrings.Where(r => r.Split('=')[0] == "q").Select(r => r.Split('=')[1]).FirstOrDefault();

    return View();
}