I can get SortOrder Value in Admin Backend with SortOrder in DataObjectManager array like this:

$f->addFieldToTab("Root.Content.Mysite", new DataObjectManager(

			$this,

			'Persons',

			'PersonObject',

			array('Thumb' => 'Thumb','Name' => 'Name','Url' => 'Url','Category'=>'Category','Languages'=>'Languages','Countries' => 'Countries','SortOrder' => 'SortOrder'),

					'getCMSFields_forPopup'

			));

I have no idea how to increment the value in this Page Model. How can i access SortOrder before addFieldToTab?

I added a function to the corresponding Data Object.

Like described in datamodel http://doc.silverstripe.org/sapphire/en/topics/datamodel i have overwritten the getSortOder funct.

function getSortOrder() {
      
      // SortOrder is not working
      //return $this->SortOrder;

     return->Name;
}

But i can not access the field SortOrder. With Name, like in the code it works.

i thought it could be perhaps

$this->Sort
$this->Order

but don't work.

I have not defined SortOrder, this field is from Dataobjectmodel auto generated per _config.php

SortableDataObject::add_sortable_class('PersonObject');

In Admin Backend first element shows nothing because SortOrder=0. That's why i like to override getSortOrder with - something like -

return ($this-SortOrder+1);