How to Zip File in Silver light

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using ICSharpCode.SharpZipLib.Zip;
using System.IO;

 public static void zipafolder(string sourcefile, string destfile)
        {   
            long directorySize = GetDirectorySize(sourcefile);

            if (File.Exists(destfile) == false)
            {
                System.IO.FileStream fs = System.IO.File.Create(destfile);
                fs.Close();
            }

            //zip.exe file should be present in Base Directory
            string zipfile = System.AppDomain.CurrentDomain.BaseDirectory + "zip.exe";
            
            System.Diagnostics.ProcessStartInfo i = new System.Diagnostics.ProcessStartInfo(zipfile);

            i.CreateNoWindow = true;
            string args = "";


            if (sourcefile.IndexOf(" ") != -1)
            {
                //we got a space in the path so wrap it in double qoutes
                args += "\"" + sourcefile + "\"";
            }
            else
            {
                args += sourcefile;
            }

            string dest = destfile;
            if (dest.IndexOf(" ") != -1)
            {
                //we got a space in the path so wrap it in double qoutes
                args += " " + "\"" + dest + "\"";
            }
            else
            {
                args += " " + dest;
            }

            i.Arguments = args;


            //Mark the process window as hidden so 
            //that the progress copy window doesn't show
            i.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
            System.Diagnostics.Process p = System.Diagnostics.Process.Start(i);
            int size = Convert.ToInt32(Convert.ToInt32(directorySize));

            System.Threading.Thread.Sleep(40000);
            
        }