See if file path is inside a directory
===

How can I check whether a path to a file that doesn't necessarily exists points to a location inside a particular directory? Say I have a method:

    bool IsInside(string path, string folder)
    {
        //...
    }

Then, if I call it like:

    IsInside("C:\\Users\\Dude\\Hi", "C:\\Users\\Dude\\Hi\\SubFolder\\SubSubFolder\\tile.txt")

should return `true` (note the sub folder), but if I call it like:

    IsInside("C:\\Users\\Dude\\Hi", "C:\\Users\\Dude\\BadFolder\\SubFolder\\SubSubFolder\\tile.txt")

should return false. The only thing I can think of right now is using string's `StartsWith`, but sounds kinda hacky to me. I haven't found a native .NET method that would check this either.