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 Microsoft SharePoint ExcelDataReader 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 = "Url=https://myorg.sharepoint.com;[email protected];Password=password;File=Book1.xlsx;";

using (Microsoft SharePoint ExcelConnection conn = new Microsoft SharePoint ExcelConnection(connectionString)) {
  Microsoft SharePoint ExcelCommand cmd = new Microsoft SharePoint ExcelCommand("SELECT * FROM Account WHERE Industry = 'Floppy Disks'", conn);
  Microsoft SharePoint ExcelDataReader 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 = "Url=https://myorg.sharepoint.com;[email protected];Password=password;File=Book1.xlsx;"

Using conn As New Microsoft SharePoint ExcelConnection(connectionString)
  Dim cmd As New Microsoft SharePoint ExcelCommand("SELECT * FROM Account WHERE Industry = 'Floppy Disks'", conn)
  Dim rdr As Microsoft SharePoint ExcelDataReader = 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