Just personal style, I guess, but I hate having 2 files for my WCF Services. I tend to like to copy/paste the interface into the .cs file so that I only have to deal with a single file.
Any dangers in doing this?
Not dangers per se - but there are times when it is very useful to have a separate assembly with your service, operation and data contracts (just the contracts, the interfaces, basically) - when you need to share those between the server and the client side.
There's really no point in sharing the whole service implementation code (the actual service class, that implements the service interface), with the client.
Plus: if you have your interfaces in a separate file (and possibly assembly), it makes it easier to write unit tests, especially if you want to mock a service. Gets a bit messy if you mix interface and class into a single file.
So I consider it a useful and helpful best practice to have separate files for interfaces and implementations (actually: always one class per file only), and to put all service- and data contracts (and fault contracts) into a separate assembly.
Actually, I like to go beyond two files, and have two separate projects. One project holds the interface definition. The primary value is for integration testing. I like to make a third project with a WCF client. That client accesses the interface in the "shared" assembly.
Remember the mantra of Testivus: "When writing the (production) code, think of the test; When writing the test, think of the code."
Related
I am currently in the process of developing a Web Service which should expose a relatively large number of ways to interact with it.
For example, Clients may be able to interact with the Web Service in order to manage users or projects in a Database.
To that effect, I created the following classes:
Two Data Contracts: IUsersServiceContract and IProjectsServiceContract
Two Service Contracts Interfaces: IUsersServiceContract and IProjectsServiceContract
My question is the following:
Does it make sense to create two different Web Services, each with their own endpoint(s), instead of creating one big class that implements both Service Contracts Interfaces ?
Keep in mind that in reality I would have many more Service Contracts Interfaces that deal with different sorts of data.
From what I understand, using a partial class (split in multiple files) will allow me to create one big Web Service with only one Endpoint.
This has the disadvantage of dealing with one big class split in multiple files, i.e: its harder to maintain and more prone to errors if developers "don't see the big picture".
The other solution would be to have one Web Service per Service Contract Interface implemented.
In essence, if I have X Service Contracts Interfaces, I end up with X Web Services with X Endpoints.
Which solution would you choose and why ?
Thanks for your input !
Personally I would not use partial classes for splitting a class; the sheer size motivating tgis split suggests that the class is too large and needs a refactoring. In my opinion partial classes main purpose is to add changes to auto generated code.
Since service and endpoint configuration can be shared using named behaviours in web.config splitting the service should not be that cumbersome. But the split should be motivated by grouping of functionality.
Without knowing the exact nature of you services it sounds like there could be a natural separation in two services; one for user related operations and one for project oriented operations.
If the implemantation classes grows above what you think are reasonable sizes I would consider letting separate classes - or preferably interfaces - handle each methods inner logic and let the service implementation it self be a shallow facade that delegates its own method parameters to the correct logoc instance
An important thing to consider here, when you're talking about n number of service contracts, is the cost associated with implementing each service contract. There's a good blog post on that here, "Service Contracts Factoring and Design", although if it wasn't Juval Lowy who posted this article then someone is clearly ripping him off (I am referring to Juval's book - "Programming WCF Services" page 93).
My understanding is that all contract-implementing code has to be in a single class, that can become very large, obviously. How do I avoid this? I really prefer to have a few small classes doing one part of the communication with clients than a single behemoth class.
The only idea I could think of is using multiple interfaces implemented by a single class split up by partial, but I don't think this is really solving the issue.
You might want to use Inheritance, depending on the structure of yoru code. Usually you can break all code up into smaller pieces, helpers, sub-routines, etc.
It's like with any other API-development, you don't want / don't need everything in the same place in the same package.
First, if your contract is big, can they be refactor into more specific service contracts?
The contract implementation class can be implemented as entry point method. You can always model the implementation and define the appropriate abstraction and have your service contract implementation class calls those internal implementation.
If you could change your code fundamentally, you could expose just a single endpoint that works with request/response messages. This way there could be a single end-point and a single service definition that takes a (possibly derived) request message and returns a response message. Your interface into the service would then just be a single method and in the server side implementation you would route that request object to the actual service implementation (possibly determined by a factory) possibly using metadata on the request message (or even it' type-name) to define what service is being called.
So, your end service interface would just have a method like this:
public interface IServiceRequestor
{
Response ProcessRequest(Request request);
}
This allows you to handle a possibly unlimited number of exposed services without having to know what they will be at compile/dev time, and also avoid a proliferation of Service methods defining the service calls available
That 'single class' usually is a facade, just a communication front-end.
So you should not implement all your logic in the Service implementor.
And your interfaces should be as small as possible (do 1 thing well). But if necessary your facade can call on multiple classes.
We have about 60 partial files called "BeamServer.cs", each in a sub-folder that corresponds to the purpose of the functions in that file. Any helper classes (or other helper files) that are for the same area of our program resides in that folder as well.
Your "one class" represents your "one business need". We found a nice side benefit in that if one of the members of our team is working on the "Accounting" portion of BEAM (our software), then they would check out the file "Accounting\BeamServer.cs" and none of the rest of the team would be effected.
EDIT: Also, the class should only contain the method signatures (and wrapper functions that simply call base.Channel.DoSomething()... Any data structures would of course be their own class files (such as "Person.cs" or "Employee.cs" or whatever).
I have a self hosted TCP based WCF service. I am now building a project that consumes that service, but there seems to be at least two ways of adding a service reference to a project and the both produce wildly different proxies. First I used the "Add service reference" from the project menu, but this generated quite a few files and even some XML schemas of the core .Net types. Then I tried the SvcUtil which only produced two files, one proxy and one config file that holds the service reference and binding parameters, this is much better but...
In both cases the VS tools seem to reproduce type definitions even though I have provided a reference to the assembly containing the service and all the types it uses. For example, some of my service methods return generic collections of Entity classes. All the Entity classes are defined within an assembly that I have directly referenced from the consuming project so why redefine those types again?
I would be grateful if some body could offer some advice on consuming WCF services that return Entity types and any best practices they follow.
We have found that the add service reference creates alot of unneeded code that gets in the way more than it helps.
We have gone over to a manual way of setting it up, there is an introduction to this method here:
http://perseus.franklins.net/dnrtvplayer/player.aspx?ShowNum=0103
Yes, in your concrete case this may seem like duplication - but consider this: WCF is also designed to be interoperable, and in MOST scenarios, especially if you have a non-.NET client calling your code, you won't have the assembly with the contract and the interfaces available.
So there's really nothing BUT creating a full proxy, that contains all that information, in order to work in all possible circumstances.
Now if you really want to avoid duplication of data contracts etc., you can compile those into their own assembly, and then use the /r:(assembly name) switch when calling svcutil to tell it to re-use the code and contracts in that assembly.
Marc
WCF promotes good design by using interfaces and contracts etc. What baffles me is that, for example in my case if I have 2 sets of business functionality like ICustomerMgmtBIZ
and IProductMgmtBiz. If these two are ServiceContracts, and I have an interface like
IBusinessService:IProductMgmtBIZ,ICustomerMgmtBIZ
and implementation class BusinessService. I see that BusinessService class will be having too much implementation. The workaround I have been using so far is by implementing partial classes.
So bluntly put, can a WCF service have only 1 implementation and 1 service contract ??
No, it is possible to implement more than one Service contract on a WCF Service type (the class that is attributed with the ServiceBehavior attribute), since it is just a matter of having the class implement multiple interfaces. If you are using any of the Visual Studio templates or other kinds of code generators, this may not be immediately clear. However, although you can implement more than one Service Contract interface on a Service type, it does not do you much good if you need the service, presumably a singleton in this case(?), to behave as one service. IBusinessService implies that you need all of the service's functionality to be callable from one client proxy, so that all operations may operate in the same logical session (similar to ASPX web session). If that is not the case, then you are free to define individual proxies for each contract interface, but that will also require that you support one endpoint for each contract.
Is it an absolute requirement that you can only have on WCF ServiceHost instance for your implementation? What factors are influencing your decision?
By the way, partial classes do not trouble me anymore. The idea of splitting out code into multiple files now seems rather natural. For example, storing partial classes in files like ServiceType_IProductMgmtBiz.cs and ServiceType_ICustomerMgmtBIZ.cs seems natural enough, in addition to storing the core logic in ServiceType.cs.
Finally, the following question might be of use...
WCF and Interface Inheritance - Is this a terrible thing to do?
Bluntly put, no - sort of - yes, but. Any workaround is non-optimal and involves using an "IBlank" as a master WCF interface (where your interfaces derive from IBlank), and two endpoints, one implementing IProductMgmtBIZ and the other implementing ICustomerMgmtBIZ. I don't have my dev machine in front of me, this might involve some other overrides. So, at the WCF level you're screwed unless you want to have two WCF ServiceHosts (which is perfectly reasonable).
In short, the workaround is inelegant. Its easier to have two WCF endpoints on the same port with a different extension.
I am developing a WCF web service which has become quite bloated. What techniques do you use to split up the implementation of the contract?
Well you have a couple choices:
First, you could leave it all in one class, but split up into different files using the partial class feature of C#.
Second, you could have the main service class just pass requests off to one of a number of other actual classes that are organized logically.
A third alternative is to consider refactoring to reduce the number of operations you have. Is there actually a use to all of the methods you're exposing?
Finally, you could always split up the service into multiple WCF services.
It's hard to answer your question if you don't give any more information.
Do you mean that your service interface is bloated, or the class implementation? It's hard to answer well, if I don't see the code, or have no other information, anyway, I'll try:
Notice that WCF service is basically just a regular class that implements an interface and has some attributes on its methods. So all the other good OO design rules apply to it. Think about what it does, does it have really single responsibility, if not try to outsource some of that responsibility to other classes that your service depends on. If you need a non-default constructor, use IInstanceProvider to create the service class, and supply it with its dependencies (or if you use Windsor Container use WCF Facility).
If you really want to you can streach your inheritance chain, and move some of the code to a base class. I don't do it, however and always prefer to use composition over inheritance.
Inspect your service contract, and think about how cohesive it really is. Maybe what you should do is to split it, into few smaller, more cohesive services.