SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirectory|\\Db.mdf;Integrated Security=True;User Instance=True");
SqlCommand com2 = new SqlCommand();
com2.Connection = con;
com2.CommandText = "insert tb_items (item_name, item_unit) values ('" + this.txtitemname.Text + "','" + this.txtitemunit.Text + "')";
con.Open();
com2.ExecuteScalar();