Saving DataTable rows in sql Table

You will have to loop and insert in the following way

 foreach (DataRow row in dt.Rows)
        {
            String strConnString = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
            SqlConnection con = new SqlConnection(strConnString);
            SqlCommand cmd = new SqlCommand();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "insert into persons(FirstName, LastName) values(@FirstName, @LastName)";
            cmd.Parameters.Add("@FirstName", SqlDbType.VarChar).Value = row["FirstName"];
            cmd.Parameters.Add("@LastName", SqlDbType.VarChar).Value = row["LastName"];
            cmd.Connection = con;
            try
            {
                con.Open();
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                con.Close();
                con.Dispose();
            }
        }