Performance - using Guid object or Guid string as Key

Question

When using a Guid as an index for a Dictionary, is it better to use the Guid object, or the string representation of the Guid?

Answer 1

The collections are fairly small, but they get iterated lots of times

If you are iterating, there are no key to key comparisons. If you are adding/modifying or looking up by key, then keys will be hashed and the hashes compared; only if the hashes are equal will the keys be compared.

Therefore, unless you are performing a lot of key based operations on huge dictionaries with many hash collisions the speed of key to key comparisons will not be a major factor.