The problem is the the ImageResouces.php cannot have controller, as long as i delete the controller class, every thing's fine....

though i did change class ImageResource extends DataObject to
class ImageResource extends Image, but I don't think this really matters....

Also, in order to display the image on the page, i cannot use
<% control Images %>
<img src="$Images.URL"/>
<% end_control%>

instead, it should be
<% control Images %>
<img src="$URL"/>
<% end_control%>

it seems doesn't recognize the expression $Images....though I saw a lot of examples online that did use $Images.URL.
Any one can explain a little about this?

Trying to get the image work, not luck now

ImageResource.php
<?php
class ImageResource extends DataObject
{
   static $has_one = array (
      
      'SectionPage' => 'SectionPage',
      'ImageResource'=>'Image'
      
   );
   
}

class ImageResource_Controller extends ContentController
{

}
?>
////////////////////////////////////////////////////////

SectionPage.php
class SectionPage extends Page
{
   static $has_many= array (
      'Images'=>'ImageResource'
   );
   
   
   
   public function getCMSFields()
   {
      $fields = parent::getCMSFields();
      
      
      $manager = new ImageDataObjectManager(
         $this,
         'Images',
         'ImageResource',
         'ImageResource',
         array('Title'=>'Title', 'Description'=>'Description'),
         new FieldSet(
            new TextField('Title'),
            new TextareaField('Description')
         ));
      $manager -> setAllowedFileTypes(array('jpg', 'png','gif'));
      $fields->addFieldToTab("Root.Content.Images", $manager);
      
      return $fields;
   }
}

class SectionPage_Controller extends Page_Controller
{

}

?>

Also, the ImagePage.ss i'm not sure what should I put there is this right?

<% control Images%>
$ImageResource
$Title

<% end_control %>

my bad..i type the file name wrong, should be SectionHolder.php

I m sure that the class name, controller name and the php file's name are consistent...

if I just use Image type and don't create any subclass of Image class, then i can add image, but since there's no relation between image class and the page type class, all the images are showing in the CMS, but only in CMS, i cannot display the images on the website.

frustrated....

Actually, the class name and the file name are the same. i just typed them wrong...it just doesn't work~

doing mean

$manager = new ImageDataObjectManager(
$this,
'Images',
'ImageResource',
'ImageResource',
array('Title'=>'Title', 'Description'=>'Description'),
new FieldSet(
new TextField('Title'),
new TextareaField('Description')
));
//////////////////////////////////

this is the definition of the constructor for imagedataobjectmanager

public function __construct($controller, $name = null, $sourceClass = null, $fileFieldName = null,.....)

shouldn't it be this way?