Hey Arte,
Im trying make attachment wich will work when i doubleclick on item. But there is no method in XmlAttachment for it

it is there, but it isnt enabled by default.

take a look at posts 94 and 105 in the RunUO xmlspawner thread.
http://runuo.com/forums/showpost.php?p=592562&postcount=94
It has an example of an attachment that will respond to double clicks

thank you ))