Thanks a lot for framing the question properly , my mistake i didnt wrote in a readable manner.
Yaa that is exactly what i wanted to do ,
only change is i am not concerned with the nearest Shape3D ,
but with the nearest vertice (which lies within specified range ) to the pick ray , for ex.
1.) Lets assume that working plane is XY plane with Z=0.
2) And if pick ray is formed at X=10,Y=10, Z=0 with ray going towards -Z Axis.
3) So for me any vertice at X=10 ,Y=10, and any Negative Z value is the Closet Vertice.
I would be very happy to know the efficent way , although it may be hard ,may be i'll learn something new in the process