ASP.NET列与字符串之和

本文关键字：字符串 NET ASP | 更新日期: 2024-10-21 09:02:49

我试图将列的和显示为字符串。怎么了？我从cmd得到的唯一输出。ExecuteRead（）；似乎是：系统。数据OleDb。OleDbDataReader

       protected void TotalHours() {
        DatabaseConnection.Commandstring = ("SELECT SUM ([Time]) FROM tbl_login");
        using (OleDbConnection con = new OleDbConnection(DatabaseConnection.ConString)) {
            try {
                con.Open();
                using (OleDbCommand cmd = new OleDbCommand(DatabaseConnection.Commandstring, con)) {
                    DatabaseConnection.result = cmd.ExecuteReader();
                    txt_TotalTime.Text = ("Total Time: " + DatabaseConnection.result.ToString());
                    con.Close();
                }
            }
            catch (Exception ex) {
                con.Close();
                Debug.WriteLine("Error Selecting Time from Database " + ex.Message);
            }
        }
    }

ASP.NET列与字符串之和

您不需要ExecuteReader，它通常用于通过读取器读取多个返回的记录。您需要的是类似ExecuteScalar的

  DatabaseConnection.result = (decimal) cmd.ExecuteScalar();

请记住将其强制转换为所需类型。它应该是十进制的，因为看起来你是在根据金钱进行计算。

如果ypu想要使用reader，您必须读取:reader.Read()；不要忘记也处理读取器（将其放入using）：

try {
  using (OleDbConnection con = new OleDbConnection(DatabaseConnection.ConString)) {
    con.Open();
    using (OleDbCommand cmd = new OleDbCommand(DatabaseConnection.Commandstring, con)) {
      using (var reader = cmd.ExecuteReader()) {
        if (reader.Read()) // you have to read
          txt_TotalTime.Text = String.Format("Total Time: ", reader.GetValue(0));
      }
    }
  }
}
catch (DbException ex) { // Bad style: do not catch ALL the exceptions
  Debug.WriteLine("Error Selecting Time from Database " + ex.Message);
}
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