expose age range in views but DOB field is date I want to expose an age range in a view (select registered users of age between 25-50) . I tried birthday module and also tried adding a Date of Birth field to user profile using Profile2 Module .

And I think Views Contextual Range Filter works with ranges (25--100) not with dates .

any ideas ? 
thanks
Try using the Computed Field module (in beta in 7). You would simply add a new field, of say age, and of Computed type, (follow a walkthrough here) and then use a Filter in the View to select the range of ages that you require.

Hope this helps!