How to create dynamic Query DSL for Includes

[Koi_Kin]

I have this query:

.Search<Person>("person", s => s
    .Index("person")
    .Source(s => s
        .Includes(i => i
            .Fields(
                f => f.Id,
            )
        )
    )
    .Query(q => q
        .Match(m => m
            .Field(personname)
            .Query(search)
        )
    )
)

and I try to make include dynamic with if-else in the code below:

public Func<SourceFilterDescriptor<Person>, ISourceFilter> PersonIncludeBuilder
{
    var fields = new List<Func<FieldsDescriptor<Person>, FieldsDescriptor<Person>>>();
    fields.Add(f => f.Field(f => f.Id));

    if(includePersonName)
    {
        fields.Add(f => f.Field(f => f.Name));
    }

    return //How to convert to Func<SourceFilterDescriptor<Person>, ISourceFilter> or are they other way to do it?;
}

Am I on the right track or are they otherways to do it?