Encrypting/Decrypting a querystring value with out write any seperate class file.

Dear All,
               How to encrypt / decrypt a query string value with out writing a seperate class file. I used Server.HtmlEncode/Server.HtmlDecode and Server.UrlEncode/Server.UrlDecode. Like below but not working.
When passing query string value :
string userId = "44";
Response.Redirect("~/Result.aspx?userId="+ Server.HtmlEncode(userId));

When receiving query string value:

if(Requeset.QueryString["userId"]!=null)
{
    string UserId = Sever.HtmlDecode(Request.QueryString["userId"].ToString());
    // ------ here getting the data from database basing on this userId value.
}

I used HtmlEncode/Decode and UrlEncode/Decode but no use. userId is not encrypted in url link of solution. please anybody ...