Rich I notice that HttpUtility should work after adding the System.Web namespace. I tried the sample in msdn and it did not work for me.
this is my namespace

using System;
using System.Drawing;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Net;
using System.IO;
using System.Text; 
using System.Web ;
using sjSMSServiceManager.Class ;

this is from MSDN sample. with error on compile

D:\TEMP\ConsoleApplication3\Class1.cs(14): The type or namespace name 'HttpUtility' could not be found (are you missing a using directive or an assembly reference?)

using System;
using System.Web;
using System.IO;

   class MyNewClass
   {
      public static void Main()
      {
         String myString;
         Console.WriteLine("Enter a string having '&' or '\"'  in it: ");
         myString=Console.ReadLine();
         String myEncodedString;
         // Encode the string.
         myEncodedString = HttpUtility.HtmlEncode(myString);
         Console.WriteLine("HTML Encoded string is "+myEncodedString);
         StringWriter myWriter = new StringWriter();
         // Decode the encoded string.
         HttpUtility.HtmlDecode(myEncodedString, myWriter);
         Console.Write("Decoded string of the above encoded string is "+
                        myWriter.ToString());
      }
   }

Thanks rick