In Nhibernate hbm.xml file .what to use in byte[] type

Question

how to define in byte[] in hbm.xml

I am using nhibernate in asp.net

i have to save pdf file into sqlserve

database fields type is in sqlserver = varbinary(MAX)

in asp.net i can retrive in byte[]

what to use in hbm.xml file in propety???

thanks