Log in with facebook account in asp.net website

its very simple steps 
step 1
you have to create one app in face book 
create one fb account -> goto developer link in footer part 
click -> create new app button .
give all info about you web site. 

then they will provide API_Key And API_Secret.

step 2
create one aspx page in your application

step 3

place one button control in your page 

c#
use these code in page load event


FaceBookConnect.API_Key = "xxxxxxxxxxxxxxxxxxxxxxxx"; // user your facebook api key
        FaceBookConnect.API_Secret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
//user your facebook API_Secret
          

        string code = Request.QueryString["code"];
      
        if (!string.IsNullOrEmpty(code))
        {
            string data = FaceBookConnect.Fetch(code, "me");
            FaceBookUser faceBookUser = new JavaScriptSerializer().Deserialize<FaceBookUser>(data);
            faceBookUser.PictureUrl = string.Format("https://graph.facebook.com/{0}/picture", faceBookUser.Id);
            Session["code"] = code;
            Session["Uid"] = faceBookUser.Id;
            DataTable ds = b.CheckEmail_signup(faceBookUser.Email);
            if (ds.Rows.Count == 0)
            {
                Int64 intLID = Convert.ToInt64(faceBookUser.Id);
                p.v_FName = faceBookUser.first_name;
                p.v_Lname = faceBookUser.last_name;
                p.v_Email = faceBookUser.Email;
                p.v_Photo = faceBookUser.PictureUrl;
                p.v_Gender = faceBookUser.gender;
                if (b.fbclientinfo_insert(intLID, p.v_FName, p.v_Lname, p.v_Email, p.v_Photo, p.v_Gender, "Approve","True") == "Success")
                {
                    Response.Redirect("home.aspx");
                }
            }
            else
            {
                Response.Redirect("home.aspx");
            }

        }
button click event

paste these code

 FaceBookConnect.Authorize("user_photos,email", Request.Url.AbsoluteUri.Split('?')[0]);

Create one model like 


public class FaceBookUser
    {
        public string Id { get; set; }
        public string first_name { get; set; }
        public string last_name { get; set; }
        public string PictureUrl { get; set; }
        public string Email { get; set; }
        public string gender { get; set; }
        public string birthday { get; set; }
    }