Hello,

I have a DataObject like this:

class MyDataObject extends DataObject {
    private static $db = array( ...  );
    private static $many_many = array(
        'Members' => 'Member'
    );
}

I manage MyDataObject with ModelAdmin. No problem.

I've make an extension:

class MyDataObjectRole extends DataExtension {
    private static $db = array( ... );
    private static $belongs_many_many = array(
        'MyDataObjects' => 'MyDataObject'
    );

    public function updateCMSFields(FieldList $fields) {
        $fields->removeByName('MyDataObjects');

        $mydataobjects = MyDataObject::get()->map('ID', ... );
        $mydataobjectfield = new ListboxField('MyDataObjects', 'MyDataObjects', $mydataobjects);
        $mydataobjectfield->setMultiple(true);

        $fields->addFieldToTab('Root.Main', $mydataobjectfield);
        return $fields;
    }
}

And i use it:

---
Name: extensions
---
Member:
  extensions:
    ['MyDataObjectRole']

In my admin Member form, i see the ListboxField and it works. OK.

But i would like to append a button like GridFieldAddNewButton after my ListbofField to facilitate new MyDataObject creation without going to ModelAdmin.

And i'm lost :)
Somebody can help me ? Thanks

Could you not use a GridField in stead of a ListBoxField? In a separate tab for instance?

Thanks for your proposal but I would like something simple, lighter than a 'big' GridField. I just need to select zero, one or more MyDataObjects. It's OK with the ListboxField. And, with a simple button, I just need to create a new MyDataObject if the object does not exist to link it to the edited or created member.

I found an extension : https://github.com/sheadawson/silverstripe-quickaddnew. I don't like the use of a popup but it works :)