Sort options when using NEST API with ElasticSearch

Implementing a sort in my query, how can I set IgnoreUnmapped(true) when using NEST API? The default value is false, which means if the field doesn't exist it won't return any results, using NEST how to change the default value?

And is there any option when sorting with NEST to be able to sort with raw query? like FilterRaw()? SortRaw()?