This works fine when the walk length is exactly 10 (which I appreciate is the length given in the instructions). However, it would be risky for future updates if (for example) the walk length were to be increased.

This would fail in some cases. For example, the code would accept the following as a valid walk when it is not valid: {"n","e","w","n","w","n","e","w","n","w"}

This doesn't work if there are multiple spaces between words in the phrase

For example, the string "most   trees are  blue" should be changed to "Most   Trees Are  Blue" but with this code it causes a System.IndexOutOfRangeException error.