ADO.NET Provider for Open Exchange Rates

Build 21.0.7930

Querying with the DataReader

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

Using the OpenExchangeRatesDataReader

The OpenExchangeRatesDataReader retrieves data faster than the OpenExchangeRatesDataAdapter because it can retrieve data in pages. As you read data from the OpenExchangeRatesDataReader, 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 Projects table:

C#

string connectionString = "AppId=abc1234;";

using (OpenExchangeRatesConnection connection = new OpenExchangeRatesConnection(connectionString)) {
  OpenExchangeRatesCommand cmd = new OpenExchangeRatesCommand("SELECT * FROM Projects", connection);
  
  OpenExchangeRatesDataReader rdr = cmd.ExecuteReader();

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

VB.NET

Dim connectionString As String = "AppId=abc1234;"

Using connection As New OpenExchangeRatesConnection(connectionString)
  Dim cmd As New OpenExchangeRatesCommand("SELECT * FROM Projects", connection)

  Dim rdr As OpenExchangeRatesDataReader = cmd.ExecuteReader()

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

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Build 21.0.7930