How to get term frequency from search result in Lucene.Net

Question

Hi, I would like to get the term frequency for a specific field from search result. How to achieve this? For instance:

My search result have 100000 hits. I m having a field called FromID and Category

Now I want the frequency for each and every fromid for a specific category as like

[email protected] 1000 docs for the category X
b.yahoo.com  200 docs for the category Y