public static System.Web.UI.WebControls.ListItemCollection GetContacts(string UserName,string Password,string Directory)

{
    System.Web.UI.WebControls.ListItemCollection ReturnArray = new System.Web.UI.WebControls.ListItemCollection();
    string server = "http:/ /ExchangeServer";
    NetworkCredential credentials = new NetworkCredential(UserName, Password);
    string uri = string.Format("{0}/exchange/{1}", server, credentials.UserName);
    byte[] contents = System.Text.Encoding.UTF8.GetBytes(string.Format(

       @"<?xml version=""1.0""?>

        <g:searchrequest xmlns:g=""DAV:"">

            <g:sql>

                SELECT

                    ""urn:schemas:contacts:givenName"", ""urn:schemas:contacts:sn"",

                    ""urn:schemas:contacts:email1""

                FROM

                    Scope('SHALLOW TRAVERSAL OF ""{0}/exchange/{1}/contacts""')

            </g:sql>

        </g:searchrequest>",

      server, credentials.UserName));

    HttpWebRequest request = HttpWebRequest.Create(uri) as HttpWebRequest;
    request.Credentials = credentials;
    request.Method = "SEARCH";
    request.ContentLength = contents.Length;
    request.ContentType = "text/xml";

    using (System.IO.Stream requestStream = request.GetRequestStream())
        requestStream.Write(contents, 0, contents.Length);

    using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
    using (System.IO.Stream responseStream = response.GetResponseStream())
    {
        XmlDocument document = new XmlDocument();
        document.Load(responseStream);
        foreach (XmlElement element in document.GetElementsByTagName("a:prop"))
        {
            if (element["d:sn"] != null && element["d:givenName"] != null && element["d:email1"] != null)
            {
                System.Web.UI.WebControls.ListItem TempItem = new System.Web.UI.WebControls.ListItem();
                TempItem.Text = element["d:sn"].InnerText+", "+element["d:givenName"].InnerText;
                TempItem.Value = element["d:email1"].InnerText;
                ReturnArray.Add(TempItem);
            }
        }
    }
    return ReturnArray;
}

        public static byte[] GetFreeBusy(string People, DateTime StartTime, DateTime EndTime, int Interval, string UserName, string Password)
        {
            string EmailAddresses = "&u=SMTP:" + People;

            //Make sure to switch this to point to your exchange server
            string Url = "exchangeserver/public/?cmd=freebusy&start=" + StartTime.Date.ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss") + "-05:00&end=" + EndTime.AddDays(1).Date.ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss") + "-05:00&interval=" + Interval.ToString() + EmailAddresses;

            System.Net.HttpWebRequest Request;
            System.Net.WebResponse Response;
            System.Net.CredentialCache MyCredentialCache;

            byte[] bytes = null;
            System.IO.Stream ResponseStream = null;
            XmlDocument ResponseXmlDoc = null;
            XmlNodeList DisplayNameNodes = null;

            try
            {
                MyCredentialCache = new System.Net.CredentialCache();
                MyCredentialCache.Add(new System.Uri(Url),
                   "NTLM",
                   new System.Net.NetworkCredential(UserName, Password, "")
                   );

                Request = (System.Net.HttpWebRequest)HttpWebRequest.Create(Url);

                Request.Credentials = MyCredentialCache;

                Request.Method = "GET";
                Request.ContentType = "text/xml; encoding='utf-8'";
                Request.UserAgent = "Mozilla/4.0(compatible;MSIE 6.0; " +
                    "Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1)";
                Request.KeepAlive = true;
                Request.AllowAutoRedirect = false;

                Response = (HttpWebResponse)Request.GetResponse();
                ResponseStream = Response.GetResponseStream();

                ResponseXmlDoc = new XmlDocument();
                ResponseXmlDoc.Load(ResponseStream);

                DisplayNameNodes = ResponseXmlDoc.GetElementsByTagName("a:item");

                if (DisplayNameNodes.Count > 0)
                {
                    for (int i = 0; i < DisplayNameNodes.Count; i++)
                    {
                        XmlNodeList Nodes = DisplayNameNodes[i].ChildNodes;
                        foreach (XmlNode Node in Nodes)
                        {
                            if (Node.Name == "a:fbdata")
                            {
                                bytes = new byte[Node.InnerText.Length];
                                for (int x = 0; x < Node.InnerText.Length; ++x)
                                {
                                    bytes[x] = byte.Parse(Node.InnerText[x].ToString());
                                }
                            }
                        }
                    }
                }
                else
                {
                    throw new Exception("Could not get free/busy data from the exchange server");
                }
                ResponseStream.Close();
                Response.Close();
                return bytes;

            }
            catch (Exception ex)
            {
                throw new Exception(ex.ToString());
            }
        }

public static string GetUsersEmail(string User, string UserName, string Password)
{
   string EmailAddress = "";
   DirectoryEntry Entry = new DirectoryEntry("LDAP://exchangeserver",   //Make sure to point this at your exchange server
                                               UserName,
                                               Password,
                                               AuthenticationTypes.Secure);
   DirectorySearcher Searcher = new DirectorySearcher(Entry);
   Searcher.PropertiesToLoad.Add("mail");
   string Filter = String.Format("(&(objectcategory=user)(cn=" + User + "))");

   Searcher.Filter = Filter;
   Searcher.Sort.Direction = SortDirection.Ascending;
   Searcher.Sort.PropertyName = "cn";

   SearchResultCollection Results;

   Results = Searcher.FindAll();

   foreach (SearchResult Result in Results)
   {
      ResultPropertyCollection Properties = Result.Properties;
      foreach (string Key in Properties.PropertyNames)
      {
         if (Key == "mail")
         {
            foreach (object Values in Properties[Key])
            {
               EmailAddress = Values.ToString();
            }
         }
      }
   }
   return EmailAddress;
}