how to auto login after registration in asp.net - asp.net

Question

I want to login automatically after registration by using a session like Session["ud"] , but I don't know where should I put it.
public partial class index : System.Web.UI.Page
{
SqlConnection cnn = new SqlConnection(ConfigurationManager.AppSettings["dbpath"]);
protected void btnSave_Click(object sender, EventArgs e)
{
long idx;
SqlCommand cmd = new SqlCommand();
cmd.Connection = cnn;
cmd.CommandText = "Insert into tblUser (UInfo,UEmail,UName,UPass, UGender) Values (#P1,#P2,#P3,#P4,#P5) select ##Identity";
cmd.Parameters.AddWithValue("#P1", txtInfo.Text);
cmd.Parameters.AddWithValue("#P2", txtEmail.Text);
cmd.Parameters.AddWithValue("#P3", txtUserName.Text);
cmd.Parameters.AddWithValue("#P4", txtPass.Text);
cmd.Parameters.AddWithValue("#P5", rdbMale.Checked);
cnn.Open();
idx = Convert.ToInt64(cmd.ExecuteScalar()); // i think here we can do something
cnn.Close();
here we want to upload the image of user and it works correctly
string fn = "";
if (FileUpload1.HasFile == true)
{
fn = FileUpload1.FileName;
string des = Server.MapPath("\\UserImg\\") + idx.ToString() + ".jpg";
FileUpload1.PostedFile.SaveAs(des);
SqlCommand cmdUpdate = new SqlCommand();
cmdUpdate.Connection = cnn;
cmdUpdate.CommandText = "Update tblUser Set UImg=#P5 where UId=#P0";
cmdUpdate.Parameters.AddWithValue("#P5", idx.ToString() + ".jpg");
cmdUpdate.Parameters.AddWithValue("#P0", idx);
cnn.Open();
cmdUpdate.ExecuteNonQuery();
cnn.Close();
}
Response.Redirect("Profile.aspx");
}
}

Answer 1

once you have entered data into in sql database you will get id of new user here
idx = Convert.ToInt64(cmd.ExecuteScalar()); // i think here we can do something
Once you get the id assign it to your session
idx = Convert.ToInt64(cmd.ExecuteScalar()); // i think here we can do something
cnn.Close();
Session["ud"]=idx;
once you have assigned session ,you just have to redirect to required page and validate Session variable if it's null or not.
i hope on Profile.aspx page you are checking for same session variable.
Profile.aspx.cs--on page load
if (Session["ud"] != null)
{
//successfull login
}
else
{
//redirect to login page
}