Not able to get value through parameter using WCF service

Hi,

I am trying to get the value through WCF service parameter 

Before this i have tested by below sql query 

select MenuTitle from dbname where ParentId='1'

Now I need the same result through below WCF service url

http://hostname:portno/_vti_bin/PresidentsService.svc/GetPresidentById/1

But I am getting blank page,please let me know if I am missing anything here.

//IPresidentsService.cs

[ServiceContract]
    interface IPresidentsService

{

 [OperationContract]
        [WebGet(UriTemplate = "GetPresidentById/{id}",
            ResponseFormat = WebMessageFormat.Json)]
        President GetPresidentById(string id);

}

//President.cs

public class President
    {
        [DataMember]
        public string Id { get; set; }

}

//PresidentsService.svc.cs

public class PresidentsService : Barkes.Services.Presidents.ISAPI.IPresidentsService

{

private List<President> Presidents
        {
            get
            {
                // If there aren't any presidents in our list, populate with samples
                _presidents = _presidents ?? new List<President>(SampleData.SamplePresidents);                
                return _presidents;                             
            }
        }

        public President GetPresidentById(string id)
        {
            var query = from President p in Presidents
                        where p.Id == id
                        select p;

            return query.FirstOrDefault();


        }

}

//PresidentsData.cs

public static class SampleData

{

        public static President[] SamplePresidents = new President[]
        {
            new President{ Id=GetLeftMenuParentId("1")}               

        };

private static string GetLeftMenuParentId(string parentid)
        {
            SqlConnection con = new SqlConnection("Data Source=dbservername;Initial Catalog=dbname;User ID=userid;Password=password");
            con.Open();
            SqlCommand cmd = new SqlCommand("select MenuTitle from dbname where ParentId="+parentid, con);
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            sda.Fill(ds);
            cmd.ExecuteNonQuery();
            con.Close();
            DataTable dt = ds.Tables[0];
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            List<Dictionary<string, object>> rows = new List<Dictionary<string, object>>();
            Dictionary<string, object> row;
            foreach (DataRow dr in dt.Rows)
            {
                row = new Dictionary<string, object>();
                foreach (DataColumn col in dt.Columns)
                {
                    row.Add(col.ColumnName, dr[col]);
                }
                rows.Add(row);
            }
            return serializer.Serialize(rows);

        }         

}

Regards,

Sudheer

Thanks & Regards, Sudheer