[AX 2012] An example of "how to attach a document to a record"?

Hi,

i need to find a working example inside AX to attach a file to a record. 

Let me explain:

I have a form (a part from the built-in ones..) with various fields about some instruments. 

One of these fields should contain a document, a file, attached by the user. 

I need to physically store it into the database. 

Hope someone could help me finding a working example. 

Thank you in advance

ciao