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 EmailDataReader 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 = "Port=993;Server=outlook.office365.com;Password=password;User=user;Protocol=IMAP;SMTP Port=587;SMTP Server=smtp.office365.com;";

using (EmailConnection conn = new EmailConnection(connectionString)) {
  EmailCommand cmd = new EmailCommand("SELECT * FROM [INBOX] WHERE Subject = 'Test'", conn);
  EmailDataReader 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 = "Port=993;Server=outlook.office365.com;Password=password;User=user;Protocol=IMAP;SMTP Port=587;SMTP Server=smtp.office365.com;"

Using conn As New EmailConnection(connectionString)
  Dim cmd As New EmailCommand("SELECT * FROM [INBOX] WHERE Subject = 'Test'", conn)
  Dim rdr As EmailDataReader = 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