WCF - call method from service implementation - wcf

Question

What I'm trying to do is the following:
1) I have the following WCF service contract:
[ServiceContract]
public interface IUploadService
{
[OperationContract]
ServiceData Upload(Request request);
}
[DataContract]
public class Request
{
[DataMember]
public long AbnNumber;
[DataMember]
public string Email;
}
2) This contract is implemented like this.
public class UploadService : IUploadService
{
public bool Upload(Request request)
{
// Some code
}
}
In the "Some code" section I would like to call a validation class to validate the clients request, so something like this:
var result = validation.ValidateRequest(request);
So my question is: Is it a bad idea to create an instance of my validation class inside the Upload method? Like this:
public class UploadService : IUploadService
{
public bool Upload(Request request)
{
var validation = new Validation();
var result = validation.ValidateRequest(request);
}
}
I know you can get around this by creating a constructor but as far as I know you can't create a constructor inside a WCF service implementation class, or am I wrong?
I'm new to WCF so if I'm totally heading the wrong direction please let me know.
Thanks

Answer 1

Personally I like as little as possible in my service methods. I would have a separate project to handle the Upload. This then allows you to reuse this code more easily, and to test the functionality without creating the service.
As to whether you should create your Validation like this it really depends on what it does, but generally I would make sure the Validation class implements an interface containing ValidateRequest(Request) and then inject that. You can then mock it in your tests if you need to.
So your service code would look like
public class UploadService : IUploadService
{
private readonly IUploadHandler _uploadHandler;
public UploadService(IUploadHandler uploadHandler)
{
_uploadHandler = uploadHandler;
}
public bool Upload(Request request)
{
//would possibly do some mapping here to create a different type of object to pass to the handler
_uploadHandler.Upload(request);
}
}
and the handler in a different project would look like
public class UploadHandler : IUploadHandler
{
private readonly IValidation _validator;
public UploadHandler(IValidation validator)
{
_validator = validator;
}
public bool Upload(Request request)
{
return _validator.ValidateRequest(request);
}
}

Answer 2

So my question is: Is it a bad idea to create an instance of my validation class inside the Upload method?
It comes down to whether you will be using Singleton or Per Call services. Usually it is better to have new instance of Service created for every request, and in that case it is OK to create all instances in your operation.
Interesting discussion on this topic Should WCF service typically be singleton or not?
If you decide to not to create Validation class for each then request there are two options:
Make it singleton
Create custom ServiceHostFactory for your service and initialize your Service in it (with constructor). Useful links on this topic:Extending Hosting Using ServiceHostFactory, Integrating StructureMap with WCF