OracleDataReader reader.Read() 从第二个记录行开始读取行，跳过第一行记录

Question

I have a SQL command and it returns 8 rows from the database.

When I use reader.Read() it starts at the second line, so I loose the fist row result. I don't know why it's skipping the first row record.

command.CommandText = "SELECT ATTRIBUTE_DESCRIPTION, SUBSTR(ATTRIBUTE_DATATYPE, 2, 6) FROM " + proj.PID_Schema + "PIDD.ATTRIBUTES@" + proj.PID_Database + " WHERE " +
                "attribute_name LIKE 'Controller' " +
                "OR attribute_name LIKE 'Initials' " +
                "OR attribute_name LIKE 'IOType' " +
                "OR attribute_name LIKE 'NetworkType' " +
                "OR attribute_name LIKE 'SignalOutput' " +
                "OR attribute_name LIKE 'SignalInput' " +
                "OR attribute_name LIKE 'SPIInstrumentType' " +
                "OR attribute_name LIKE 'Substation' ORDER BY 1";

            try
            {
                reader = command.ExecuteReader();
                reader.Read();

                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        codelistsNumbersDict.Add(reader.GetValue(0).ToString(), reader.GetValue(1).ToString());
                    }
                }
            }
            catch (Exception)
            {
            }

            connection.Close();

            return codelistsNumbersDict;
        }

Answer 1

Do you have two reads:

reader = command.ExecuteReader();
reader.Read(); // <--- FIRST READ (skipe first row)

if (reader.HasRows)
{
    while (reader.Read())  // <---- SECOND READ
    {

Because of this, you starting reading on second row.

If you take a look to Retrieve data using a DataReader sample, it only has one read:

SqlDataReader reader = command.ExecuteReader();
                   // <-- No read here on sample!
if (reader.HasRows)
{
    while (reader.Read()) // <-- Just ONE READ
    {

Doc screenshot:

Answer 2

As mentioned in @dani-herrera's answer, you are calling reader.Read() twice.

Also, you don't need the if (reader.HasRows) , since if there are no rows the code inside the do loop won't execute. If you need to know the rows processed, you can always add a counter.

            try
            {
                reader = command.ExecuteReader();

                while (reader.Read())
                {
                    codelistsNumbersDict.Add(reader.GetValue(0).ToString(), reader.GetValue(1).ToString());
                }
            }