Q:

MVC Business logic helper

I have some common functions that apply throughout my application to update particular parts of the database when actions happen (Audit trail, modified dates etc). I'll use AuditTrail as an example.
Where should I be storing these functions?
Currently I am storing them in dbcontext classes
//... my db context class ...

public bool AddAuditEntry(int ID, string objectName)
{
    // Here I create a new AuditTrail object, assign values then insert into db.
    // This mode doesn't have a controller.
}

// We also have a table that keeps track of modified state for 
// client side caching (nothing I have control over)
public bool ModifyObject(int ID)
{
    // Here I mark the object id with modified date then save to db
    // This particular model doesn't have a controller either.
}

I think they should belong in the model but I'm not quite sure how to implement it. Putting them in the controller isn't the best option as some of these relate only to a particular model class that may have no controller.
My problem with them being in the model is what then is the best way to update entities?

A:

I'm not sure if this is the way other people do it but I actually have two models. I have my business models which contain these kinds of functions and validations. Stuff like an account balance cannot be less than zero or something like that. Once all that's done the models are translated into database models which are responsible for database level validations if necessary and database operations.

