求教，label.text 赋值无法显示解决方案

求教，label.text 赋值无法显示
求教各位大侠，下列代码中将数据库中 总价 列 求和后 赋值给 label2.text ，form框体上数值无法显示。求帮忙看看哪里有问题
  private void label2_Click(object sender, EventArgs e)
  {
  OleDbConnection conn = new OleDbConnection();
  String str = "./db1.mdb";
  OleDbConnection OleDbcon = new OleDbConnection("Provider=Microsoft.jet.OLEDB.4.0;Data Source=" + str + ";User ID=admin;Password=;Jet OLEDB:Database Password=");
  OleDbcon.Open();  

  OleDbCommand cmd = new OleDbCommand();
  cmd.Connection = OleDbcon;
  string s = label2.Text;
  string select = String.Format("SELECT 总价 FROM sheet1 union all SELECT sum(总价) FROM sheet1", s);
  cmd.CommandText = select;
  OleDbDataReader reader = cmd.ExecuteReader();
  reader.Read();
  label2.Text = reader.GetString(0);
  }





[解决办法]
if(reader.Read())
{
label2.Text = reader.GetString(0);
}
[解决办法]
跟一下代码，这种事情，基本上都是因为你的sql没有读到结果！
目测，是因为你的sql问题！
[解决办法]
label2.Text = reader[0].ToString();