I have a factory class which imports a list of IOperation types. I get the following error when I try and resolve the factory class:
Resulting in:
Cannot activate part
'Message36Operation'. Element:
Message36Operation -->
Message36Operation --> DirectoryCatalog
(Path=".\")
Resulting in:
Cannot get export 'Message36Operation
(ContractName="IOperation")' from part
'Message36Operation'. Element:
Message36Operation
(ContractName="IOperation") -->
Message36Operation --> DirectoryCatalog
(Path=".\")
Resulting in:
Cannot set import
'OperationsFactory.Operations
(ContractName="IOperation")' on part
'OperationsFactory'. Element:
OperationsFactory.Operations
(ContractName="IOperation") -->
OperationsFactory --> AssemblyCatalog
(Assembly="RmiToODKMessanger, Version=1.0.0.0,
Culture=neutral, PublicKeyToken=null")
Here's what I have:
[Export(typeof(OperationsFactory))]
public class OperationsFactory
{
[ImportMany(typeof(IOperation))]
private IEnumerable<IOperation> Operations { get; set; }
}
public interface IOperation
{
}
public abstract class BaseRmiOperation : IOperation
{
}
[Export(typeof(IOperation))]
public class Message36Operation : BaseRmiOperation, IOperation
{
}
The exception is thrown will I try and resolve an instance of the factory.
I can get this to work if I remove the abstract class.
Any ideas,
Thanks,
Ken
** Update:
Below is the BaseRmiOperation class. I'm instantiating a few classes in the cstor and that's it.
I forgot to mention the structure of the app previously.
CG.App: contains OperationsFactory and bootstrapper class for MEF.
CG.Plugins : Contains various IOperation implementations such as Message36Operation and the BaseRmiOperation abstract class
CG.Common : Contains IOperation interface. This assembly is referenced by both CG.App and CG.Plugins
The CG.App.Bootstrapper class loads the plugins from bin/plugins.
public abstract class BaseRmiOperation : IOperation
{
protected SettingsManager _settingsManager;
protected RmiMessenger _messenager;
protected ILogger _logger;
protected TagManager _tagManager;
protected Environments _rmiEnvironment;
protected string _msgSource;
protected string _emp_id;
public BaseRmiOperation()
{
this._settingsManager = new SettingsManager();
this._messenager = new RmiMessenger(null, null);
this._tagManager = new TagManager(); // pass ILogger
//this._logger = logger;
// pulls the rmi_env and a few other settings from
// winCC.
PopulateRmiSettings();
}
public abstract ExitCodes Execute(object[] data);
public abstract string Description { get; }
public abstract string Alias { get; }
Sorted the problem. Silly mistake. The TagManager assembly was not present in the /bin folder and was causing the BaseRmiOperation cstor to crash. A breakpoint at the start of the cstor was never being called, it always crashed on the line to resolve the OperationFactory. Figured it out by going back to basics and adding functionality one line at a time. Thanks.
Related
I'm running a C# project on VS2019 with the following code structure:
In the Class1.cs file:
public class Class1
{
public class MyClass2 : Class2
{
...
}
private void RunAlgorithm<T>() where T : Class2, new()
{
T argInstance = new T();
...
}
static void Main(string[] args)
{
RunAlgorithm<MyClass2>();
}
}
In the Class2.cs file:
public class Class2
{
public Class2() { }
public string setParameters { get; set; }
}
I'm getting the following error for the line RunAlgorithm<MyClass2>();
'Class1.MyClass2' must be a non-abstract type with a public
parameterless constructor in order to use it as parameter 'T' in the
generic type or method 'Class1.RunAlgorithm()'
even if I change it to Public, the error persists
Well, minimally, it'll have to be protected so that MyClass can access it..
https://dotnetfiddle.net/XFeEdQ
public class Class1
{
class MyClass2 : Class2
{
}
private void RunAlgorithm<T>() where T : Class2, new()
{
T argInstance = new T();
}
public static void Main(string[] args)
{
new Class1().RunAlgorithm<MyClass2>();
}
}
public class Class2
{
protected Class2() { }
public string setParameters { get; set; }
}
So your "Class1.MyClass2
must have a public parameterless constructor" message is saying that your MyClass needs a constructor. Mine above has such a constructor even though it's not in the code; in the absence of the developer providing a constructor the compiler provides one that does nothing other than call the base parameterless constructor...
...which leads me to the next point; your MyClass2 extends Class2, and hence Class2's constructor needs to be accessible to it. While Class2's constructor is private, MyClass2's constructor can't call it. Every constructor on c# has to either call another constructor or a base constructor. If you don't specify which, the compiler will insert a call to base() for you, which will fail if the base constructor is inaccessible
For this all to work out you need a public parameterless constructor in MyClass2:
public MyClass2():base(){}
or without the base(compiler will add the base call)
or blank (compiler will add all of it)
and you need something that makes Class2's constructor accessible to MyClass2, ie declaring Class2's constructor as public or protected
I am building an EntityFramework/WebApi back end.
I want to decouple my WebApi from the Entity Framework, and utilize Dependency Injection so I can swap out the "data source" for the web API.
I have been looking at the Unit of Work and Repository patterns.
I also want to use breezejs.
The breezejs TempHire samples has been alot of help, so I will use this as an example for my question -
https://github.com/Breeze/breeze.js.samples/tree/master/net/TempHire
In this sample, on the data side we have the UnitOfWork class -
public class UnitOfWork
{
private readonly EFContextProvider<TempHireDbContext> _contextProvider;
public UnitOfWork()
{
_contextProvider = new EFContextProvider<TempHireDbContext>();
StaffingResources = new Repository<StaffingResource>(_contextProvider.Context);
Addresses = new Repository<Address>(_contextProvider.Context);
// .. etc.
}
public IRepository<StaffingResource> StaffingResources { get; private set; }
public IRepository<Address> Addresses { get; private set; }
// .. etc.
public SaveResult Commit(JObject changeSet)
{
return _contextProvider.SaveChanges(changeSet);
}
}
Then on the WebApi side, it uses it like this -
[BreezeController]
[Authorize]
public class ResourceMgtController : ApiController
{
private readonly UnitOfWork _unitOfWork = new UnitOfWork();
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
return _unitOfWork.Commit(saveBundle);
}
// ... etc.
}
I would like to refactor to something like this, so that I could swap out the back end.
public class UnitOfWork : IUnitOfWork
public class ResourceMgtController : ApiController
{
private readonly IUnitOfWork _unitOfWork;
public ResourceMgtController(IUnitOfWork unitOfWork) {
this._unitOfWOrk = unitOfWork; // Dependency Injected...
}
// ... etc.
}
What I can't wrap my head around, is how I can make it generic. The breeze client needs a method like this -
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
return _unitOfWork.Commit(saveBundle);
}
And I can't put this in IUnitOfWork -
SaveResult SaveChanges(JObject saveBundle)
And really keep it decoupled from breeze, be able to swap out the back end for another backend. Am I attempting the abstraction at the wrong point? I guess if I want breeze on the client I will need to couple it on the backend?
You clearly can define an interface with that method:
public interface IUnitOfWork {
...
SaveResult SaveChanges(JObject saveBundle); // no problem
}
I suspect that you are objecting to the fact that both SaveResult and JObject are classes defined by libraries (Breeze.ContextProvider and Newtonsoft.Json.Linq respectively) you'd rather not reference somewhere.
These references wouldn't bother me any more than I mind referencing System.Linq to get IQueryable. In fact, a test double of SaveResult (a public class of Breeze.ContextProvider) is trivially easy to construct. Here is its definition (and the definition of KeyMapping, its only non-native dependent type):
public class SaveResult
{
public List<object> Entities;
public List<KeyMapping> KeyMappings;
public List<object> Errors;
}
public class KeyMapping
{
public string EntityTypeName;
public object TempValue;
public object RealValue;
}
But if Breeze and Newtonsoft.Json references are that noxious to you and you're willing to surrender some type safety, you can always create the interface like this:
public interface IUnitOfWork {
...
object SaveChanges(object saveBundle); // no safety, no problem
}
Then in your concrete UnitOfWork you add a suitable overload:
public object IUnitOfWork.SaveChanges(object saveBundle)
{
return SaveChanges((JObject) saveBundle);
}
public SaveResult SaveChanges(JObject saveBundle)
{
return _contextProvider.SaveChanges(saveBundle);
}
... and Bob's your uncle.
Yes, I did try it (in DocCode); worked fine for me.
I am creating a custom tag library using http://www.cqblueprints.com/xwiki/bin/view/Blue+Prints/Writing+A+JSP+Custom+Tag+Library to produce XSS-proof links from my custom components. I have taken this to a tag since I will need to do other bits of work and to avoid writing scriptlets on the JSP files (I have posted the code at the end).
I wanted to use the XSSAPI from my Java class, but looking at the javadoc for XSSAPI I see that it's an interface; when using it in a JSP file it's an object that is initialized invoking <cq:defineObjects/>.
Does anyone have any ideas on how to do this? There is a method in the XSSAPI class called getRequestSpecificAPI(slingRequest) but it's not static, and I have run out of ideas right now.
#JspTag
public class FixInternalLinkTag extends CqSimpleTagSupport {
private String pathToPage;
#Override
public void doTag() throws JspException, IOException {
XSSAPI xssAPI; // ToDo how to get a reference to this?
urlPointingToPage = xssAPI.getValidHref(urlPointingToPage);
getJspWriter().write(urlPointingToPage);
}
public String getPathToPage() {
return pathToPage;
}
#JspTagAttribute(required = true, rtexprvalue = true)
public void setPathToPage(String pathToPage) {
this.pathToPage = pathToPage;
}
}
If you make your tag class an osgi service
#Component(immediate = true, metatype = true, description = "User Group Finder")
#Service
public class MyClass { ...
you can then use
#Reference
XSSAPI xssapi;
to pull in the implementation of XSSAPI. Then you can use it
xssapi.getRequestSpecificAPI(slingRequest);
I'm building a small Nancy web project.
In a method of one of my classes (not a nancy module), I would like to basically do:
var myThing = TinyIoC.TinyIoCContainer.Current.Resolve<IMyThing>();
However, there is only one registration in .Current (non public members, _RegisteredTypes) which is:
TinyIoC.TinyIoCContainer.TypeRegistration
Naturally, in my above code, I'm getting:
Unable to resolve type: My.Namespace.IMyThing
So, I guess I'm not getting the same container registered in my bootstrapper?
Is there a way to get at it?
EDIT
To flesh out a bit more of what I'm trying to do:
Basically, my url structure looks something like:
/{myType}/{myMethod}
So, the idea being, going to: /customer/ShowAllWithTheNameAlex would load the Customer service, and execute the showAllWithTheNameAlex method
How I do this is:
public interface IService
{
void DoSomething();
IEnumerable<string> GetSomeThings();
}
I then have an abstract base class, with a method GetService that returns the service.
It's here that i'm trying to use the TinyIoC.TinyIoCContainer.Current.Resolve();
In this case, it would be TinyIoC.TinyIoCContainer.Current.Resolve("typeName");
public abstract class Service : IService
{
abstract void DoSomething();
abstract IEnumerable<string> GetSomeThings();
public static IService GetService(string type)
{
//currently, i'm doing this with reflection....
}
}
Here's my implementation of the service.
public class CustomerService : Service
{
public void DoSomething()
{
//do stuff
}
public IEnumerable<string> GetSomeThings()
{
//return stuff
}
public IEnumerable<Customer> ShowAllWithTheNameAlex()
{
//return
}
}
Finally, I have my Nancy Module, that looks like:
public class MyModule : NancyModule
{
public MyModule()
{
Get["/{typeName}/{methodName}"] = p => ExecuteMethod(p.typeName, p.methodName);
}
private dynamic ExecuteMethod(string typeName, string methodName)
{
var service = Service.GetService(typeName);
var result = service.GetType().GetMethod(methodName).Invoke(service, null);
//do stuff
return result; //or whatever
}
}
#alexjamesbrown - The short answer is, you don't. Nancy was specifically designed so that you did not deal with the container directly. You mention that the class, that you want to take a dependency on IMyThing, is not a NancyModule. Well this is not an issue, as long as one of your modules has a reference to it, then those dependencies can also have their own dependencies that will be satisfied at runtime.
public interface IGreetingMessageService
{
string GetMessage();
}
public class GreetingMessageService: IGreetingMessageService
{
public string GetMessage()
{
return "Hi!";
}
}
public interface IGreeter
{
string Greet();
}
public class Greeter
{
private readonly IGreetingMessageService service;
public Greeter(IGreetingMessageService service)
{
this.service = service;
}
public string Greet()
{
return this.service.GetMessage();
}
}
public class GreetingsModule : NancyModule
{
public GreetingModule(IGreeter greeter)
{
Get["/"] = x => greeter.Greet();
}
}
The above will work just fine and Greeter will have it's dependency on IGreetingMessageService satisfied at runtime
I have had a very similar issue, needing to "share" the container. The reason this is an issue is that my program runs as a service using Nancy self hosting to provide a REST API. My modules have dependencies which are injected by Nancy itself, but the other parts of the app which are not referenced from modules also need dependencies injected.
Multiple containers are not a sensible option here (or anywhere really), I need to share the container between Nancy and the rest of the app.
I simply did the following
(I'm using Autofac but I suspect that TinyIoC in similar)
public class Bootstrapper : AutofacNancyBootstrapper
{
private static readonly Lazy<ILifetimeScope> container = new Lazy<ILifetimeScope>(RegisterTypes);
public static ILifetimeScope Container => container.Value;
protected override ILifetimeScope GetApplicationContainer()
{
return container.Value;
}
// Create container and register my types
private static ILifetimeScope RegisterTypes()
{
var builder = new ContainerBuilder();
// Register all my own types.....
return builder.Build();
}
}
Then, in my main code, I can use the container myself
public class Program
{
public static void Main(string[] args)
{
// Resolve main service with all its dependencies
var service = Bootstrapper.Container.Resolve<Service>();
service.Run();
}
}
As my NancyHost is within the Service, the container is constructed (once) upon its first use in main, this static is then used when Nancy gets round to creating the Bootstrapper itself.
In an ideal world, I wouldn't really want a globally accessible container, normally it would be local to the main function.
In this particular case "not dealing with the container directly" is highly problematic:
public interface IFoo {}
public class Foo : IFoo { public Foo(string bar) {} }
Assume IFoo already is a constructor dependency of a Nancy module.
Note the Foo constructor's string dependency. I need to communicate to the container to use that constructor for an IFoo singleton, when encountered as a Nancy module dependency. I need to register that on the TinyIoC instance NancyFx uses, and pass in the actual value of bar.
i write silverlight program very simple.i use Mef and WCF.
this code is MainPageViewModel class that included Commands and properties.
public List<NoOfStudentsDropDownItem> ListNoOfStudent{get;set;}
public MainPageViewModel()
{
InitializList();
}
private void InitializList()
{
ListNoOfStudent.Add(New NoOfStudentsDropDownItem(){DisplayText="1",NoOfStudent=-1});
ListNoOfStudent.Add(New NoOfStudentsDropDownItem(){DisplayText="5",NoOfStudent=5});
}
this is NoOfStudentsDropDownItem class;
public Class NoOfStudentsDropDownItem
{
public string DisplayText{get;set;}
public int NoofStudent{get;set}
}
this is part of App Class.
private void Application_Startup(object sender,StartupEventArgs e)
{
CompositionInitializer.SatisfyImports(this);
MainPage mainpage=new MainPage();
mainpage.DataContext=MainViewModel;
this.RootVisual=mainpage;
}
[Import]
public MainPageViewModel MainViewModel{get;set;}
i haven't error when commented InitializList method.i dont know cause.
You simply forgot to create the list. You declared a property for it, but it is never assigned so it will still be null when you call Add.