I am trying to filter out empty string fields on my db

when i try query = e => e.Bool(b => b.Must(m => m.Term(m => m.Field(field).CaseInsensitive(true).Value("123"))));

its gives me the record where field value is 123.

my db also contains lists that has empty field values.
so when I run this
query = e => e.Bool(b => b.Must(m => m.Term(m => m.Field(field).CaseInsensitive(true).Value(""))));
the query is not being generated

I get all records both empty and non empty field records