Object recognition through csharp

Question

Hi
I would like to build an image search system, that can match both
colors and/or shapes.
The pictures will be quite simple picture with normaly 4-10 colors
(maybe 20 in extreme cases)like an object .
Large areas with the same color (no photographs) or extremely details.
 what technique should I use, has anyone done this in c# and sql server?
The picture database will probably contain millions of pictures when
its done, the pictures wont be very large, probably 200-300 pixels in
height and width.

thanx