Is it okay to hit the database from a custom model binder?

Question

Say I have an object that gets some data from HttpPost and some from the database. I think I want to allow the ModelBinder to go to the database/repository for the that data missing from the post. In practice, is this a good or bad idea?

Answer 1

I've decided to edit my original answer given my thinking on these types of things has evolved since early 2010.

In my original answer, I basically expressed that, while my instincts told me you shouldn't do this, I was uncomfortable saying we shouldn't without being able to articulate why.

Now, I'd recommend against this on the grounds that the responsibility of a Model Binder is to translate a user request into a Request Model and that retrieving data outside of what can be derived from the request goes beyond this scope of responsibility.

Answer 2

I would say a bad idea. The idea of the model binder is that it takes the parameters from the request and creates your model from those. If your model binder, behind the scenes, fills in some of the details from the database this breaks the paradigm. I'd much rather expose the database call in my controller by explicitly fetching the required extra data from the database directly. Note that this could be refactored into a method if used frequently.