Hello,
I have added a custom TextField into CMS of a DataObject

function getCMSFields() {
  $fields = parent::getCMSFields();
  ...
  $fields->addFieldToTab('Root.Main', new TextField('MyField', 'My custom field'));
 ..
}

And I do not want how ti access to it (value, etc) from other method like function ManageMyField(). I have tried a lot of variations but none works.. Do you have an idea?

You've added a field to the CMS, but you've not hinted at adding it to the model.

• If you wish to access the data later, then you will need to create a field on the model.
  
• If you wish to use this field to obtain information to modify before storing, then perhaps a hiddenfield and some javascript onchange to this field you've already added to store the value would be an acceptable solution.
  
• If you want to store information on the model, but not have the field show in the CMS, simply add the field to the model (private static $db) but do not insert the field to the edit form via the getCMSFields() function.

Thanks for the reply.
I want to use it to create another DataObject with it's value and I thought I can just get if from some DataObject's methods and use it in onBeforeWrite() for example.
I am new in SilverStripe so I do not know much, by creating a field on the model you mean creating some private $field?