EF代码优先模型上的自定义属性

Question

Currently using EF 6 in a new project. I've been using EF for sometime now, so am pretty familiar with it - at the very least as the average user of it.

We are looking to split storage of data between SQL (eventually Azure SQL) and Azure Table Storage.

The reason for the split is some of the data on an entity just isn't suitable for a relational database. For example, we have some clients that prefer contact's to have properties A,B,C,D and another client prefers to have F,G,H,I,J,K,L - so it would make more sense to store this part of the data in a NoSql solution so we're not constraining ourselves, rather than adding dozens of columns in a table to handle varying requirements on that model.

We're currently, in the new build, serializing/deserializing these sets of data which is ok, though not ideal. Especially given it can be expensive performing this task on every read/write.

So - that leads me to my question. (no code to show at this time)

I figured I would be able to decorate specific properties on some data models with a custom attribute, such as [NoSqlStore] and then react to these. I can, for example, override the SaveChanges() method in EF to save data to the appropriate table store should any property on the entity contain the attribute.

The hard part, at least what I'm struggling with at the moment, is how to handle reads from the database. I would, ideally, like to be able to listen for (or override) something in EF that is fired when data is being fetched. Is there such an event/method built into EF for this? I figure if i can intercept EF when it's populating my model I can then react to any attribute decoration.

Answer 1

In EF6 you can use the command interception mechanism where the interceptor is invoked each time the command is being executed. You can also modify results if needed (might be a bit cumbersome though). This article is a good starting point. Another way to go about it is to look at the ObjectContext.ObjectMaterialized event and populate properties that are not populated by EF in the handler for this event.