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

Using the ParquetDataAdapter

Use the adapter's Fill method to retrieve data from the data source. An empty DataTable instance is passed as an argument to the Fill method. When the method returns, the DataTable instance is populated with the queried data. Note that the ParquetDataAdapter is slower than the ParquetDataReader because the Fill method needs to retrieve all data from the data source before returning.

The following example selects the Id and Column1 columns of the SampleTable_1 table:

C#

string connectionString = "URI=C:\folder\table.parquet;";

using (ParquetConnection connection = new ParquetConnection(connectionString)) {
  ParquetDataAdapter dataAdapter = new ParquetDataAdapter(
  "SELECT Id, Column1 FROM SampleTable_1", connection);

  DataTable table = new DataTable();
  dataAdapter.Fill(table);

  Console.WriteLine("Contents of SampleTable_1.");

  foreach (DataRow row in table.Rows) {
    Console.WriteLine("{0}: {1}", row["Id"], row["Column1"]);
  }
}

VB.NET

Dim connectionString As String = "URI=C:\folder\table.parquet;"

Using connection As New ParquetConnection(connectionString)
  Dim dataAdapter As New ParquetDataAdapter("SELECT Id, Column1 FROM SampleTable_1", connection)

  Dim table As New DataTable()
  dataAdapter.Fill(table)

  Console.WriteLine("Contents of SampleTable_1.")

  For Each row As DataRow In table.Rows
    Console.WriteLine("{0}: {1}", row("Id"), row("Column1"))
  Next
End Using