I am building a WCF service.
The Data Contract objects will be the exact same as the Business Objects.
Should I create Data Contracts in my WCF service or reference my BO Layer and use those Business Objects in my WCF Operations?
I would split them in different projects:
Foo.DataContracts
Foo.BusinessModels
Foo.Services
Reference BusinessModels and DataContracts in Services. Then map the model classes to contract classes using AutoMapper and vice versa. You can then later change your models without breaking your WCF clients, since they rely on the contracts.
If your business objects can be serialized without muddling the concerns of serialization in with the business logic, then I'd say go for it.
A better alternative though is to bring your business logic layer behind the Services layer and expose simple DTOs from the service that your view can bind to.
I wrote an article on this approach with WCF RIA Services that translates pretty well to standard WCF Web Services
I think in the same line of #valpolushkin though I have not used AutoMapper till now.
See my answer in WCF Message & Data Contract, DTO, domain model, and shared assemblies for an example where the use of Business Entities as Data Contract can cause breaking changes.
I think, it is a very bad practice to use Business Objects as DataContracts. The Service need to be autonomous. The service may be used by clients that has / has not got Lax Versioning.
Refer Service Versioning.
It is easy to mistakenly believe that adding a new member will not break existing clients. If you are unsure that all clients can handle lax versioning, the recommendation is to use the strict versioning guidelines and treat data contracts as immutable.
Also, refer MSDN - Service Layer Guidelines
Design transformation objects that translate between business entities and data contracts.
Related
I have a set of custom entities which reflect the business representation of data. Then I also have a set of entities that map 1-to-1 to the database that represent the storage of the data. My business layer converts between the 2 types and performs any other logic needed. I only expose the custom objects through my service interface.
From what I can tell I cannot use WCF Data Services. Data services
need to be bound directly to a db source (or some slight abstraction of the direct db connection) and,
that results in using the data entities.
Correct me if I'm wrong, but I can't see any way to use WCF Data Services and its built-in queryability with custom entities while using my business layer.
I do not necessarily agree with that. If you look at the Architecture Overview in http://msdn.microsoft.com/en-us/library/cc668794.aspx you see two other options next to the EF / DB connectivity. You can have Data Service Providers that just take an alternative (your custom) information model made up of queryable CLR classes and expose them using WCF data services.
So if you create your Business Layer using this approach, your custom entities can just as easy be exposed with WCF data services.
I have an existing set of Services and Repositories I use in an MVC application that leverage the Entity Framework 4.1 Code First.
I want to create a couple of WCF Services that use the existing architecture, but it seems to have a hard time serializing the object graphs.
I realize that there are some circular references to deal with, but I really don't want to litter the Domain Objects with WCF attributes, so should I just create View Models like my MVC app uses? And if so, should I create the View Models to be able to be used in both?
Any other ideas? - Thanks!!
I prefer keeping my domain model and the WCF data contract separate by defining Data Transfer Object classes as the data contact of the WCF server. They are tailored specifically to carry the right data across the wire. A good DTO design will keep the number of WCF service call roundtrips from the client down. It will also separate your internal domain model from the contract with the client.
I have just started evaluating whether or not I should be using OData influenced wcf data services or a standard WCF service application as the primary data source for Silverlight applications. I would like your thoughts on which is a better way under what situation/circumstance. What is lighter over the wire, easier to maintain, etc.
What I have gathered so far is:
There are no Wcf data service templates in VS2010 that I know of, and I will need to create a asp.net web project first and then add a wcf data service, so its going to affect how I structure my projects.
WCF Data services expose actual table names over the service. I don't know yet of a way I can alias them and I'm not sure its a good idea to let the world know my table structure
In a standard wcf service I will need to write linq queries against the EF or Domain service classes on the service side, while in a data service I can move that processing logic to the client.
At first glance examining the classes exposed by the wcf data services seem easier to read and understand than those exposed by the EF
Do add your thoughts on this..
Thanks for your time.
There are no Wcf data service
templates in VS2010 that I know of,
Not project template - just an item template (for use inside an ASP.NET web site or web app). WCF DataServices are very tightly coupled to HTTP, so they only make sense in a web site/app.
WCF Data services expose actual table
names over the service.
NO ! At least not necessarily. The whole point of EF is that you can decouple the actual physical structure of your database from the (conceptual) model that gets exposed. You can totally rename entities, you can map several entities onto a single table, split up an entity over several tables, you can leave out attributes - anything you like!
At first glance examining the classes
exposed by the wcf data services seem
easier to read and understand than
those exposed by the EF
I doubt it - because by default, WCF Data Services will use a Linq-to-SQL or EF model as their basis, really. You can make that as simple or as complicated as you like.
Using a "regular" WCF service allows you to use the netTcpBinding for much faster performance (thanks to binary message encoding vs. textual messages for other bindings), when using your Silverlight 4 app in a company-internal network (doesn't work for internet scenarios) - not something you can do with WCF DataServices.
The main difference in my opinion is the SOAP vs. REST difference:
SOAP (traditional WCF) is oriented towards methods - you think and design your system in terms of methods - things you can do (GetCustomer, SaveOrder etc.)
REST (the WCF DataServices approach) is all about resources, e.g. you have your resources and collections of resources (e.g. Customers) and you expose those out to the world, with standard HTTP verbs (GET, POST, PUT, DELETE) instead of separate specific methods that you define
So both approaches have their pros and cons. I guess the most important question is: what kind of app are you creating, and what kind of user audience are you targetting?
Update:
for intranet / internal apps, I would think the advantage of a netTcpBinding (binary encoding) would justify using a classic WCF service - also for data-intensive apps, I personally find a method-based approach (GetCustomer, SaveCustomer) to be easier to use and understand
for a public-facing app, using HTTP and being as interoperable as possible is probably your major concern, so in that scenario, I'd probably favor the WCF Data Service - easy to use, easy to understand URLs for the user
I have 2 contracts (cA & cB) implemented by a single WCF service with 2 endpoints (epA & epB).
This is not for security purposes, but purely for reasons of clarity/organization, I'd like to only "see" ContractA's operations when I discover the service via endpointA; and likewise, only see ContractB's operations via endpointB.
I don't need to "protect" these operations per se. The scenario is such that any given client only needs one "side" of the service, never both (but, the operations themselves share resources, so it makes sense to have a single service rather than 2 services).
It seems that any given service basically gets 1 WSDL, ergo all operations are exposed to all endpoints. Is that the way it works, or is there a way to "shape" an endpoint by occluding operations not defined by the endpoints contract?
By default, you're right - one service implementation class gets one WSDL which contains all service methods (from all service contracts) that this service class implements.
There are no ways present (as far as I know) to "shape" the WSDL in any (easy) way - WCF does offer ways to get into the process of creating the WSDL (statically or dynamically), but those aren't for the faint of heart. It would be much easier for you to just split the implementation of the service contracts into two separate classes and then you'd have two separate services, separate WSDL's and all.
Marc is absolutelly right. I'm just adding why this happens in WCF. In WCF all metadata related functionality are based around service metadata behavior and mex endpoint. Both these features are defined on service level. So you can't take higher granuality (unless you write a lot of custom code) and specify metadata per endpoint.
WCF service (class) is directly mapped to wsdl:service element which exposes each contract as separate wsdl:port (in WCF known as endpoint). This is the main point in answering your question. If you don't want your second contract in that wsdl:service you can't implement it in the same class.
You have mentioned that your service contracts share resources. In that case your WCF service probably also contains business logic. That is a reason for your problems. The good design for implementing WCF services is to create them only as wrappers around separate business logic classes.
Assume a situation where a data will never be queried directly. AKA, there will always be some filtering logic and/or business logic that must occur.
When is a good reason to use data services outside of ajax/js?
Please don't site this page http://msdn.microsoft.com/en-us/data/bb931106.aspx
Your essentially asking what layer of abstraction should I use, WCF Data Services is built on top of WCF and aims to simplify the process of creating a REST based service that is consumable by anything on the web. It takes away a lot of the plumbing and configuration required to do this with a standard WCF service. The querying feature is another big plus and something that is difficult to get right with standard WCF.
So in short:
If you want to quickly build a loosely typed service that wraps an existing data model and enables querying support give WCF Data Services a go.
If you want full control over the service contract or the flexibility of exposing the service over any protocol, stick with plain old WCF.