Few correction in below inline SQL queries:
SqlCommand cmd1;
cmd1 = new SqlCommand("SELECT * FROM User_table WHERE User_ID = '" + Session["UserId"].ToString() + "'", cn1);
SqlCommand cmd;
cmd = new SqlCommand("SELECT * FROM Billing_Address WHERE User_ID= '" + Session["UserId"].ToString()+"'", cn);
Although above one resolve your problem stills it has
SQL Injection problem, so always use parameterised query like below:
SqlCommand cmd1;
cmd1 = new SqlCommand("SELECT * FROM User_table WHERE User_ID = @UserID", cn1);
cmd1.Parameters.AddWithValue("@UserID", Session["UserId"].ToString());