How write query for getting last 3 months records in linq to sql?

How write query for getting last 3 months records in linq to sql?

I want to display last 3 months sales records.Based on current month will
show it's previous records in linq to sql.Please tell me the query for
that.
If current month is june then will show apr,may,june records.
id name no.ofsales desc
1 test 12 test desc
2 test1 16 desc message
Give me idea on this query.