Soft Shelled Crabs in DC or Metro accessible DC?
Try "Crisfield Seafood Restaurant" on Georgia Avenue in Silver Spring, but the end of the season may be approaching quickly.
I recently had the soft shell platter - four small crabs, lightly breaded, fries and slaw for $24.
They also do a sandwich (I believe it's about $12) with sides.
I would estimate it's about a 15-minute walk south from the Silver Spring Metro station on the Red Line.