The CData ADO.NET Provider for HarperDB implements two ADO.NET interfaces you can use to retrieve data from HarperDB: HarperDBDataAdapter and HarperDBDataReader objects. Whereas HarperDBDataAdapter objects retrieve a single result set of all the data that matches a query, HarperDBDataReader objects fetch data in subset increments as needed.

Using the HarperDBDataReader

The HarperDBDataReader retrieves data faster than the HarperDBDataAdapter because it can retrieve data in pages. As you read data from the HarperDBDataReader, it periodically requests the next page of results from the data source, if required. This causes results to be returned at a faster rate. The following example selects all the columns from the [HarperDB].[cstest].Cutomers table:

C#

string connectionString = "Server=127.0.0.1;User=admin;Password=1234;Port=9925;";

using (HarperDBConnection connection = new HarperDBConnection(connectionString)) {
  HarperDBCommand cmd = new HarperDBCommand("SELECT * FROM [HarperDB].[cstest].Cutomers", connection);
  
  HarperDBDataReader rdr = cmd.ExecuteReader();

  while (rdr.Read()) {
    Console.WriteLine(String.Format("\t{0} --> \t\t{1}", rdr["City"], rdr["CompanyName"]));
  }
}

VB.NET

Dim connectionString As String = "Server=127.0.0.1;User=admin;Password=1234;Port=9925;"

Using connection As New HarperDBConnection(connectionString)
  Dim cmd As New HarperDBCommand("SELECT * FROM [HarperDB].[cstest].Cutomers", connection)

  Dim rdr As HarperDBDataReader = cmd.ExecuteReader()

  While rdr.Read()
    Console.WriteLine([String].Format(vbTab & "{0} --> " & vbTab & vbTab & "{1}", rdr("City"), rdr("CompanyName")))
  End While
End Using