Hi Aph,

Please see a sample code below

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using WebApplication3.devWsdl;

namespace WebApplication3
{
    public partial class _Default : System.Web.UI.Page
    {
        SforceService svc = new SforceService();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindContacts();
            }
        }
        public bool IsSFDCLogin()
        {
            try
            {
                LoginResult objLoginResultr = svc.login("narasimha@gmail.com", "lakshmi@123lLzsm8ORK3tUxaJrUEoXKIop6");
                SessionHeader objSessionHeader = new SessionHeader();
                objSessionHeader.sessionId = objLoginResultr.sessionId;
                svc.SessionHeaderValue = objSessionHeader;
                svc.Url = objLoginResultr.serverUrl;
                return true;
            }
            catch (Exception ex)
            {
                return false;
            }
        }


        private void BindContacts()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Name");
            dt.Columns.Add("LastName");
            dt.Columns.Add("Phone");
            dt.Columns.Add("Email");
            dt.Columns.Add("Fax");
            dt.Columns.Add("Id");
            dt.AcceptChanges();

            if (IsSFDCLogin())
            {
                var objResult = svc.query("select id,name,LastName,Phone,Email,Fax from contact");
               

                if (objResult.size > 0)
                {
                    for (int i = 0; i < objResult.size; i++)
                    {
                        DataRow dr = dt.NewRow();
                        dr["Id"] = ((Contact)(objResult.records[i])).Id;
                        dr["Name"] = ((Contact)(objResult.records[i])).Name;
                        dr["LastName"] = ((Contact)(objResult.records[i])).LastName;
                        dr["Phone"] = ((Contact)(objResult.records[i])).Phone;
                        dr["Email"] = ((Contact)(objResult.records[i])).Email;
                        dr["Fax"] = ((Contact)(objResult.records[i])).Fax;
                        dt.Rows.Add(dr);
                    }
                    dt.AcceptChanges();

                    gvTest.DataSource = dt;
                    gvTest.DataBind();
                }
            }
        }

    }
}

Please let me know if this helps

Best Regards
Naga Kiran