How to select all object with Vray material in scene

In case someone needs a script for the same purpose.
Here is a fast, dirty and functional script (thanks to Anubis)

--Destroy the dialog if it is already open 
try(destroyDialog roll_matselection)catch()

-- UI STUFF
rollout roll_matselection "Material Selector V1.0"
(
		group "Select Materials:"
		(
		button btn_VRay "Select Object with VRay Materials" height:22 width:190 tooltip:"Select Object with VRay Materials" align:#center
		button btn_Standard "Select Object with Standard Materials" height:22 width:190 tooltip:"Select Object with Standard Materials" align:#center
		button btn_MentalRay "Select Object with MentalRay Materials" height:22 width:190 tooltip:"Select Object with MentalRay Materials" align:#center
		button btn_Brazil "Select Object with Brazil Materials" height:22 width:190 tooltip:"Select Object with Brazil R/S Materials" align:#center
		)
		
		HyperLink hl_homepage "..:: Raymond H. Ingebretsen ::.." address:"http://www.homme3d.com/" color:(color 255 255 255) hovercolor:(color 111 111 111) visitedcolor:(color 255 255 255) align:#center


	-- select all objs with VRay mat's
	on btn_VRay pressed do
	(
		select (for o in objects where o.mat.category == #vray collect o)
	)
	
	on btn_Standard pressed do
	-- select all objs with standard mat's
	(
		select (for o in objects where o.mat.category == #standard collect o)
	)

	on btn_MentalRay pressed do
	-- select all objs with mr mat's
	(
		select (for o in objects where o.mat.category == #mental_ray collect o)
	)

	on btn_Brazil pressed do
	-- select all objs with brazil mat's
	(
		select (for o in objects where o.mat.category == #Brazil_r_s collect o)
	)

) -- End Rollout

-- Create Dialog Stuff
createDialog roll_matselection 210 160 pos:[150,150] 

The solution you came up with did the job, so i used this with VRay:

select (for o in objects where o.mat.category == #vray collect o)

Thank you so much :)

EDIT: The purpose was to select all objects in the scene with Vray materials, and fix them to arc_and_design for rendering with Mentalray.

What your

vray_materials

array hold? If their're classes then your code would work fine. Also may try ".category" property of the material. Examples:

-- select all objs with standard mat's
select (for o in objects where o.mat.category == #standard collect o)

-- select all objs with mr mat's
select (for o in objects where o.mat.category == #mental_ray collect o)

-- select all objs with brazil mat's
select (for o in objects where o.mat.category == #Brazil_r_s collect o)

I not work with VRay, so just select 1 vr-mat and get the category from it ;) Cheers!