I am trying to add a dropdown populated by another dataobject (Company) to the MemberTableList (Security Tab)

The DataObjectDecorator:

class Customer extends DataObjectDecorator {
	
	static $summary_fields = array(
		'CompanyID' => 'Company'
	);
	
	function extraDBFields() {
		return array(
			'has_one' => array(
				'Company' => 'Company'
			)
		);
	}
	
	public function updateCMSFields(FieldSet &$fields) {
	   
		$companies = DataObject::get("Company")->toDropdownMap('ID', 'CompanyName');
		$fields->push(new DropdownField("CompanyID", "Company", $companies));
   }
   
   public function updateSummaryFields(&$fields)
   {
   		$companies = DataObject::get("Company")->toDropdownMap('ID', 'CompanyName');
		$fields->push(new DropdownField("CompanyID", "Company", $companies));
   }
}

The Company dropdown is added to to the popup and works fine but I can not get it added to the tablelist what am I doing wrong?

Any help much appreciated!!!

If one of the dev's could comment on this would be much appreciated there is no clear example I can find doing this seeing that MemberTableField::addMembershipFields is deprecated an also will not let you change the field types this would be really handy I am willing to write a tutorial on this for the wiki if I can get this working.

I've got a number of sites with this issue now, does anyone have any documentation on how to add a field to the MemberTableList now that MemberTableField::addMembershipFields has been deprecated for 2.4?????

Did we manage to find out how to do this? Adding fields to the Member Table field that is.

You need to use Object::add_extension to extend the Member class and then you use the updateSummaryFields function.
There is a bit more of a detailed explanation here:
http://chillburn.com.au/blog/adding-summary-fields-to-the-membertablelist-using-silverstripe-2-4/