CODEWITHSUNDEEP
c#entity-frameworkasp.net-web-apiasp.net-core
Kyle V.
Kyle V.

Reputation: 4792

Filtering with Web API

I have an application with several Web API controllers and I now I have a requirement which is to be able to filter GET results by the object properties. I've been looking at using OData but I'm not sure if it's a good fit for a couple reasons:

  1. The Web API controller does not have direct access to the DataContext, instead it gets data from our database through our "domain" layer so it has no visibility into our Entity Framework models.
  2. Tying into the first item, the Web API deals with lightweight DTO model objects which are produced in the domain layer. This is effectively what hides the EF models. The issue here is I want these queries to be executed in our database but by the time the Web API method gets a collection from the domain layer all of the objects in the collection have been mapped to these DTO objects, so I don't see how the OData filter could possibly do it's job when the objects are once-removed from EF in this way.
  3. This item may be the most important one: We don't really want to allow arbitrary querying against our Web API/Database. We just sort of want to leverage this OData library to avoid writing our own filters, and filter parsers/builders for every type of object that could be returned by one of our Web API endpoints.

Am I on the wrong track based on #3? If not, would we be able to use this OData library without significant refactoring to how our Web API and our EF interact?

Upvotes: 4

Views: 1775

Answers (1)

Steve Py
Steve Py

Reputation: 34683

I haven't had experience with OData, but from what I can see it's designed to be fed a Context and manages the interaction and returning of those models. I am definitely not a fan of returning Entities in any form to a client.

It's an ugly situation to be in, but when faced with this, my first course of action is to push back to the clients to justify their searching needs. The default request is almost always "Well, it would be nice to be able to search against everything." My answer to that is that I don't want to know what you want, I want to know what you need because I don't want to give you a loaded gun to shoot your own foot off with and then have you blame me because the system came grinding to a halt. Searching is a huge performance killer if it's too open-ended. It's hard to test for accuracy/relevance, and efficiently index for 100% of possible search cases when users only need 25% of those scenarios. If the client cannot tell you what searching they will need, and just want everything because they might need it, then they don't need it yet.

Personally I stick to specific search DTOs and translate those into the linq expressions.

If I was faced with a hard requirement to implement something like that, I would:

  1. Try to push for these searches/reports to be done off a reporting replica that is synchronized with the live database. (To minimize the bleeding when some idiot managers fire up some wacky non-indexed search criteria so that it doesn't tie up the production DB where people are trying to do work.)
  2. Create a new bounded DbContext specific for searching with separate entity definitions that only expose the minimum # of properties to represent search criteria and IDs.
  3. Hook this bounded context into the API and OData. It will return "search results". When a user selects a search result, use the ID(s) against the API to load the applicable domain, or initiate an action, etc.

no. 1. is optional, a nice to have provided they can live with searches not "seeing" updated criteria until replicated. (I.e. a few seconds to minutes depending on replication strategy/size) Normally these searches are used for reporting-type queries so I'd push to keep these separate from the normal day-to-day searching options that users use. (I.e. an advanced search option or the like.)

Upvotes: 1

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