This should work, try this:
private static bool ColumnExists(SqlDataReader reader, string columnName)
{
using (var schemaTable = reader.GetSchemaTable())
{
if (schemaTable != null)
schemaTable.DefaultView.RowFilter = String.Format("ColumnName= '{0}'", columnName);
return schemaTable != null && (schemaTable.DefaultView.Count > 0);
}
}