Why can't I do this?
internal class InsuranceClientFactory : IInsuranceClientFactory
{
internal Iws2SoapClient InsuranceClient()
{
}
}
internal interface IInsuranceClientFactory
{
Iws2SoapClient InsuranceClient();
}
I get the error:
Cannot implement an interface member because it is not public
There are a few questions where the class is public but the interface is not, but both of mine are internal. I don't want to expose this class or interface outside of my assembly. Seems an odd limitation.
This question C# internal interface with internal implementation, does state "If you are implicitly implementing an interface I believe that the member must be declared public." but this doesn't make sense to me, why can't you? seems justified?
"I don't want to expose this class or interface . . ." and that fine.
But the method needs to be public, even if it is public it won't be visible outside the assembly because the class is internal.
If you really REALLY don't want it to be public, you can explicitly implement that method.
internal class InsuranceClientFactory : IInsuranceClientFactory
{
Iws2SoapClient IInsuranceClientFactory.InsuranceClient()
{
}
}
You have to change the method modifier to public
internal class InsuranceClientFactory : IInsuranceClientFactory
{
public Iws2SoapClient InsuranceClient()
{
}
}
Making the method public doesn't mean it can be accessed publicly since the DeclaringType itself internal method will have internal access only.
I can tell you why it doesn't work. C# Language specification 5.0 section 13.4.4, Interface Mapping.
... Neither non-public nor static members participate in interface mapping ...
but because what you are attempting to do should technically work, the explicit implementation is given precedence and your implementation can remain internal
And not to split hairs, but even if you Explicitly Implement the internal interface, the implementation will not be internal it is actually private/public as stated earlier in the specification (Section 13.4.1 Explicit Interface Member Implementation):
Explicit interface member implementations have different accessibility characteristics than other members. Because explicit interface member implementations are never accessible through their fully qualified name in a method invocation or a property access, they are in a sense private. However, since they can be accessed through an interface instance, they are in a sense also public.
Change it to:
internal class InsuranceClientFactory : IInsuranceClientFactory
{
public Iws2SoapClient InsuranceClient()
{
}
}
The class is still internal and isn't exposing the interface.
Related
Interface:
interface IMyInterface{
internal int Property {get; set;}
}
Class:
public class MyClass: IMyInterface{
internal int Property {get; set;}
}
Result:
CS8704 Error: MyClass doesnot implement interface member Property.get MyClass cannot implicitly implement a non-public member.
Why I have to implement the interface explicitly?
The simple answer to "why is a language like this" is "because that's how the language designers specified it".
Now, why did they design it that way? Some of the official notes I found were these. It seems the main question was about what kind of access the implementor must have:
Would we allow non-public interface members to be implemented implicitly? If so, what is required of the accessibility of the implementing method? Some options:
Must be public
Must be the exact same accessibility
Must be at least as accessible
They decided:
For now, let's simply not allow it. Only public interface members can be implicitly implemented (and only by public members).
The "for now" never changed, so as of C# 8 an interface can have non-public virtual members but a class may only implement them explicitly.
I can speculate on a couple of reasons they may have decided against implicit overrides like this:
Non-public virtual methods in interfaces may have been considered a "rare" feature (after all, aren't interfaces supposed to document the public behavior of a class?), not worth putting a lot of resources into in terms of the semantics of implicit overrides.
Unlike with method overridding in class-to-class inheritance, an class method implementing an interface method doesn't use the override keyword. It might have been considered confusing to see a protected and/or internal method and not realize that it's fulfilling an interface contract. (Public methods are presumably considered exempt from this concern because that's the way they've always worked, and public methods are part of the class' public contract anyway so modifying / removing them would already be cause the reader to think about other parts of code that depend on it.)
Interfaces can only override other interface methods explicitly, possibly again because allowing interface-to-interface implicit implementation would be too expensive for the compiler and tooling teams and too confusing for C# users. (Especially since interface-to-interface inheritance is multiple-inheritance.) Since both this and non-public interface methods were introduced in general in C# 8, it may have made sense to make the two features match syntactically.
See also the notes on this question in the default interface method proposal.
Interface members don't have scopes like public or internal. What you have here is a default interface implementation.
So you need to remove the scope on the interface:
interface IMyInterface{
int Property {get; set;}
}
The internal property forces the implementation to be explicit such that the internal members of the interfaces will remain internal to the assembly.
It helps you to keep implementations internal (to an assembly) so that you can update code without breaking changes e.g. renaming the property.
interface IMyInterface
{
internal int Property { get; set; }
}
public class MyClass : IMyInterface
{
int IMyInterface.Property { get; set; }
}
I came across this problem when i was implementing n interface explicitly using Visual Studio. So the interface contains properties, but when I am implementing the property explicitly in an abstract class, Compiler throws error "The modifier 'public' is not valid for this item".
Refer Below given code.
interface ITest
{
bool MyProperty { get; set; }
}
internal class Test : ITest
{
public bool ITest.MyProperty
{
get
{
return false;
}
set { }
}
}
According to the programming guide, explicit interface implementations always lack an access modifier. You should remove the public keyword.
If you think about it, this makes a lot of sense. There is only one possible access modifier for an explicit interface implementation - the same modifier used for the interface. Thus, you don't need to specify the modifier.
If the interface is marked public, and the explicit implementation is private, that will not make sense. The only reason to write an explicit implementation is to expose that member to only that interface. It would be weird if the member is less accessible than the interface, right?
On the other hand, if the interface is internal and the member is marked public, it will not make sense either. If the member is more accessible than the interface, then it will not be exposed only to the interface.
I have the class ImplementationDetail which I would like to keep internal, e.g.:
internal class ImplementationDetail
{
}
I have GenericBaseClass that uses its parameter privately, e.g.:
public class GenericBaseClass<T>
{
private T useImplementationDetail;
}
And, I have a Derived class that specifies to use ImplementationDetail, e.g.:
public class DerivedClass: GenericBaseClass<ImplementationDetail>
{
}
This results in the error CS0060 Inconsistent accessibility; which is caused by ImplementationDetail being internal whereas DerivedClass is public.
How can I avoid the CS0060 compiler error while keeping ImplementationDetail internal?
Instead of using an internal class, use an interface. Then use explicit implementation on the methods you want to keep private. That way, they're never exposed.
It is not possible.
You have to use a public interface or class. See the comments of #DavidG, #Jonesopolis.
I am developing an internal class that implements an internal interface.
Can anyone explain why I cannot declare my method as internal, why I am getting the following error: "cannot implement an interface member because it is not public".
I know that I have to declare the method as public, but it makes absolutely no sense to me.
What is the point of declaring a method public if both the interface and the class are internal?
Is it not misleading?
I have read a related question on this site. It is not an exact duplicate, because my class is internal.
Simply put: because that's the way the language designers designed it. Even in internal interfaces, the methods are implicitly public. It does make things simple, but it's a pain in other ways.
If you want a public class where you want to "hide" the use of an internal interface, you could use explicit interface implementation - although that has other drawbacks.
Of course, if your class is internal then it doesn't matter that the methods are public anyway - other assemblies aren't going to be able to call the methods because they can't see the type.
I definitely agree that C# (or .NET in general) hasn't been designed as carefully as it might be around internal interfaces.
In terms of exactly why you're getting an error message - section 13.4.4 of the C# 4 spec (interface mapping) is the reason. Implementations are only found for nonstatic public members and explicit interface member implementations - and if there are any unimplemented members in the interface, an error occurs.
I know this is old but maybe someone find it useful. You can accomplish a kind of internal interface methods like this:
internal interface IFoo
{
void MyMethod();
}
public abstract class Foo : IFoo
{
void IFoo.MyMethod()
{
MyMethod();
}
internal abstract void MyMethod();
}
So all your internal classes should derive from Foo and are forced to implement the abstract MyMethod. But you can treat them all as IFoo of course. But those classes outside the assembly won't provide the MyMethod class.
So you have the advantage to treat your classes internally as IFoo and rely on MyMethod. The drawback is that all your classes will need to derive from Foo which can be a problem if you need another base class.
But I found it helpful if the abstract base class is a generic one and the interface is not. Maybe it is useful in some cases.
I'm refactoring some code I didn't write, that contains business logic and proprietary algorithms I don't want to expose. All the code is currently marked as internal; for testing purposes, and to ensure I don't break existing clients/services, I wanted to switch them to use interfaces, and implement those interfaces.
I've marked my classes as internal and their members as protected internal, and my interfaces as internal, but to use the internal interfaces, I've had to make several of my properties public.
I believe, and with some limited testing, seemed to have proven that only friend assemblies, and classes in my assembly, can use these internal interfaces and classes.
As long as both the class, and interface remain internal, even if some of the methods and the properties are marked public, will they be exposed at all?
It doesn't seem so, but I'm looking for anything I might have missed.
If you mean protected as in a using assembly can't directly use them, then yes, if the interface and class are marked internal, then they won't be visible outside the assembly. Think of the access level on the interfaces and members as being separate locks to get through.
If you can see the interface at its access level, then you can store a reference to it, and then if you can see the properties/methods at their access levels, then you can call/set/get them.
Keep in mind, though, as #phoog points out that protected internal is a bit looser than internal.
All this said, if your internal class implements a public interface, and those properties are part of a public interface as well, they could be visible... But that's really getting obscure...
public interface IVisible
{
string VisibleProperty { get; set; }
}
internal class InvisibleClass : IVisible
{
public string VisibleProperty { get; set; }
}
In the above, you could refer to the class InvisibleClass through an IVisible reference in a different assembly if you could find a way to construct or receive a reference to it (for instance, if it were returned from a factory method inside of the original assembly).
All this aside, if your question is that you want to avoid them from being examined through a decompiler, reflection, etc, that's a different question...
A public member is only as accessible as its type ("Normally, the accessibility of a member is not greater than the accessibility of the type that contains it. However, a public member of an internal class might be accessible from outside the assembly if the member implements interface methods or overrides virtual methods that are defined in a public base class.").
Don't be bitten by the protected internal problem, though: a protected internal member is available to derived classes outside the assembly.
References:
Accessibility levels: http://msdn.microsoft.com/en-us/library/ba0a1yw2.aspx
Access modifiers: http://msdn.microsoft.com/en-us/library/ms173121.aspx
You're right. Since you can't access internal classes from outside (apart from friend assemblies), you can't access any of its methods either, even if they're public.
You could access an internal class from outside it it has a public base class or implements a public interface. But you could only access the public methods in that class that are both in the base class (or interface) and overridden in the sub class (so the method should also be virtual or part of an interface - which also makes it virtual). For this, you'd have to obtain an instance to the class referenced by a super class (or interface) variable.