How to find point between two keys in sorted dictionary

Question

I have a sorted dictionary that contains measured data points as key/value pairs. To determine the value for a non-measured data point I want to extrapolate the value between t

Answer 1

I don't think there is a function on SortedDictionary that lets you find elements around the one you need faster than iterating elements. (+1 to BrokenGlass solution)

To be able to find items faster you need to switch to some other structure. I.e. SortedList provides similar functionality but allows to index its Key collection and hence you can use binary serach to find the range.