Okay, I have a solution I am working on that has 4 different projects in it. One of my projects (a console application) is trying to make reference to some of the classes defined in another project (a library); the only problem is, those called are defined as Internal in the library.
How can I use these Internal classes in other assemblies/projects in the same solution? I added references to the library, but that did not help. It is saying that the protection level is too high (because it is internal, it is only available in that assembly).
You generally shouldn't access something that's internal. That defeats the purpose of declaring it so in the first place. If, however, you do need to...
If you can change the assembly with internal things, either:
Make the classes public, or
Use the InternalsVisibleToAttribute to expose it to just the assemblies you want to.
If you cannot change it, or decide not to, then you can use reflection to access the internal classes. For some portions of what you then do with the class, you should be able to use the dynamic keyword to make access easier and faster than with reflection.
You must use reflection to access the internal classes in other assemblies, but it will be significantly slower and not generally optimizable by the compiler. It's also somewhat complicated.
It is recommended that you expose a public class that wraps your internal classes and methods from the other assembly, or simply switch the internal classes in the other assembly over to public.
Related
I want to separate platform-independent logic of my C# program into a shared project. Now I would like to hide repositories, service classes and such from my platform-specific projects. What access modifier can I use? internal doesn't seem to work, as they are compiled into the same executable (I think) and I don't want to go tag all my classes with InternalsVisibleToAttribute.
Is there a way to make classes in my shared project invisible to my platform-specific code?
There's only one place where you need to know the real type you're trying to instance - the platform provider. Everyone else should just use the interfaces that are platform-invariant.
All the platform-specific implementations can then be private or internal for all you care - you just need to ensure the provider has access. Your application will use the platform-specific provider to get the platform-specific instances, while only ever using the platform-invariant interfaces.
As for "being compiled into a single executable", that's not really important. Most likely you care entirely about compile-time checking, and that's still present regardless of how the final executable is packaged. There's some restrictions on reflection in a partial trust environment, but by that point you shouldn't care - you're only in it for the compile checks, not the runtime safety.
No, there is no such feature in C#. If you consider marking every other project with InternalsVisibleToAttribute an option, that would do the trick.
If possible, you could split off those other files (repositories, service files) to another assembly, which is not included in your shared project.
In java you have package level protection that ensures classes are only usable within the package.
Namespaces in C# act more or less like packages. But C# does not have a protection level for protecting classes within a namespace.
Is there a specific reason for this?
There is no such access modifier: the closest modifier is internal, but the unit of protection is the assembly in which the class resides, not its namespace.
One could argue that it is possible to achieve similar level of control using internal, because both kinds of restriction keep outsiders from accessing the implementation details of your library. The only person to whom it makes a difference is you, the writer of the library, and you are in full control of what to expose and what to hide anyway. Essentially, it means that if you do not want to use a class outside its namespace, simply refrain from using it; if the class is internal, nobody else will be able to use that class either.
In .NET there are assemlies(dll or exe files), you can use internal modifier to limit access only within the same assembly
Is there a specific reason for this?
Mostly, it's because there are some key differences between packages and namespaces
To simplify what's already been said in the linked question and here: Namespaces in C# are mostly to help with organizing an assembly's contents, both internally and externally. Java packages have more in common with C# assemblies, and there is an access modifier in C# that restricts to the assembly level: internal.
When implementing the facade pattern in Java, I can easily hide the subsystem of the facade by using the package-private modifier. As a result, there is only a small interface accessible from outside the facade/package, other classes of the sub-system are not visible.
As you already know, there is no package-private modifier in C#, but a similar one called internal. According to the docs, classes defined as internal are only accessible within the same assembly.
From what I unterstand, I have to create at least two assemblies (means practically two .exe/.dll files) in order to hide the subsystem of the facade physically. By physically I mean that the classes a) cannot be instantiated from outside and b) are not shown by intellisense outside the facade.
Do I really have to split my small project into one .exe and one .dll (for the facade) so that the internal keyword has an effect? My facade's subsystem only consists of 2 classes, an own .dll seems to be overkill.
If yes, what is the best practice way in Visual Studio to outsource my facade to its own assembly?
Don't get me wrong, I have no real need to split up my program into several assemblies. I just want to hide some classes behind my facade from IntelliSense and prevent instantiation from outside. But if I'm not wrong, there is no easier way that that.
Using a separate project is the general preferred approach. In fact, you often have interfaces or facades in a third assembly that both the implementation and UI assemblies reference.
That said, you can accomplish this in a single assembly using a nested private subclass.
public interface IMyService {}
public static class MyServiceBuilder
{
public static IMyService GetMyService()
{
//Most likely your real implementation has the service stored somewhere
return new MyService();
}
private sealed class MyService : IMyService
{
//...
}
}
The outer class effectively becomes your 'package' for privacy scoping purposes. You probably wouldn't want to do this for large 'packages'; in those cases, it's cleaner to move the code to a separate assembly and use internal.
Note that if you primary objection to multiple assemblies is deployment, you can actually merge multiple assemblies for the purpose of creating a simpler executable or library deployment. This way you can retain the insulation benefits of multiple projects/assemblies without having the headache of multiple files that can potentially be distributed or versioned independently.
I have two class libraries "MyLibrary.dll" and "MyLibraryEditor.dll" for a Unity runtime and editor extension. There are several class members inside "MyLibrary.dll" that are only intended for use by "MyLibraryEditor.dll".
My first thought was to use the internal keyword because I mistakenly thought that this constrained visibility to a namespace. Instead it is clear that this keyword limits visibility to the assembly.
What is the best way to constrain access to some class members to "MyLibrary.dll" and "MyLibraryEditor.dll" without hurting performance? Also, reflection is not an option.
I am happy to simply not document the functions, but unfortunately Intellisense (and MonoDevelop's equivalent) show these members.
If you want internals in one assembly to be visible from another assembly, you can use the InternalsVisibleTo attribute on the assembly containing the internals. See http://msdn.microsoft.com/en-us/library/system.runtime.compilerservices.internalsvisibletoattribute.aspx:
[assembly:InternalsVisibleTo("MyLibraryEditor")]
That answered, you might want to rethink your architectural design so that you don't need to use it, since it will open up all internals to the other assembly, not only the ones that you want.
You could make the members internal but use [InternalsVisibleTo] to give access to those members to the other assembly. They'd still be visible within the same assembly as well, of course... there's no way of getting round that.
I primarily use InternalsVisibleToAttribute for giving access to internal members to test classes, and would try to avoid doing this for non-test purposes - but sometimes it can be useful.
This is not possible using pure C# concepts. You are two seperate assemblies, that is as far seperate as you can get, and there is no relationship between the two as far as .Net is concerned.
you could do some things with signing or validation to make it so it would be difficult to use one assembly without the other, but not something you can do to prevent visibility of the classes/members.
I have an assembly which is being developed to create a facade around some potentially sensitive functionality and I want to allow a third party to call some of the methods contained within it but not others.
How can I prevent the third party calling unauthorised methods given they will have access to the entire DLL (I'm not concerned about them seeing the code, just executing it)?
This has to be compatible with the .net compact framework so unfortunately using the StrongNameIdentityPermission attribute is not possible.
I think you should ship two Facade implementations, one for 'internal' consumers which exposes all methods and another external that exposes only the sub-set. You can achieve this whilst maintaining only one code base by having two separate build processes. One technique that springs to mind is to use compiler directives to exclude a method from the external build, or mark it internal if it is required by other public methods. If you do ship sensitive methods with internal modifiers you may also want to implement obfuscation.
EDIT
Perhaps it would be cleaner, rather than having directives around each method to use partial classes, define a partial class for the sensitive methods and put the entire class implementation in a directive.
public partial class MyClass
{
public void NonSensitive(){}
}
#if INTERNAL_BUILD
public partial class MyClass
{
public void Sensitive(){}
}
#endif
You can have this partial class in the same or a separate file, which might be a nice level of separation as you could prepend the file name x_Sensitive.cs or similar.
Description
Assuming i understand your question.
You can mark your methods with the internal access modifier to make them not
accessable from other librarys.
But this does not help from security persepective, because it is always possible to run the method using reflection.
The internal keyword is an access modifier for types and type members. Internal types or members are accessible only within files in the same assembly
More Information
MSDN - internal (C# Reference)
If a third party can see the code, then they can run it - there is nothing you do to stop this.
Note however you have an application which is loading 3rd party plugins then you could load plugin assemblies with restrictions that prevent it from using reflection - this would mean that you can mark these methods / classes as internal to prevent plugins from being able to call these methods when loaded as a plugin in your application. Depending on the nature of the sensitive functionality this may or may not be useful to you from a security perspective.
For information on how to do this see How to: Run Partially Trusted Code in a Sandbox
Could you offer the functionality that you want the third party to consume as a Web API? They will not have any access to the source code OR the compiled binaries. They will only be able to see exactly what you want them to see. This would also offer additional security features such as Authentication and Authorization of callers.