The terms "width" and "height" are clearer and they match what the values actually represent (window or parent width/height). The YAML changes are generated with the update rule.
PARENT_TOP and PARENT_LEFT should be 0 so they are not very useful substitutions. They are replaced with 0 or removed if that was the whole value for a field.
- Rename the filename parameter to name and make it mandatory. Review all callers and ensure a useful string is provided as input, to ensure sufficient context is included for logging and debugging. This can be a filename, url, or any arbitrary text so include whatever context seems reasonable.
- When several MiniYamls are created that have similar content, provide a shared string pool. This allows strings that are common between all the yaml to be shared, reducing long term memory usage. We also change the pool from a dictionary to a set. Originally a Dictionary had to be used so we could call TryGetValue to get a reference to the pooled string. Now that more recent versions of dotnet provide a TryGetValue on HashSet, we can use a set directly without the memory wasted by having to store both keys and values in a dictionary.
This allows the LINQ spelling to be used, but benefits from the performance improvement of the specific methods for these classes that provide the same result.