You can access the same column information about the results of a query that you can for table schemas. See Columns for the columns returned.

Retrieving Result Set Metadata

You can use the GetSchemaTable method of the ParquetDataReader to retrieve result set metadata. Call GetSchemaTable after calling ExecuteReader.

Each row of the DataTable describes a column in the query's result.

C#

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

using (ParquetConnection conn = new ParquetConnection(connectionString)) {
  ParquetCommand cmd = new ParquetCommand("SELECT * FROM SampleTable_1 WHERE Column2 = 'Bob'", conn);
  ParquetDataReader rdr = cmd.ExecuteReader();
  DataTable schemaTable = rdr.GetSchemaTable();
  foreach (DataRow row in schemaTable.Rows) {
    foreach (DataColumn col in schemaTable.Columns) {
      Console.WriteLine("{0}: {1}", col.ColumnName, row[col]);
    }
  }
}

VB.NET

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

Using conn As New ParquetConnection(connectionString)
  Dim cmd As New ParquetCommand("SELECT * FROM SampleTable_1 WHERE Column2 = 'Bob'", conn)
  Dim rdr As ParquetDataReader = cmd.ExecuteReader()
  Dim schemaTable As DataTable = rdr.GetSchemaTable()
  For Each row As DataRow In schemaTable.Rows
    For Each col As DataColumn In schemaTable.Columns
      Console.WriteLine("{0}: {1}", col.ColumnName, row(col))
    Next
  Next
End Using