I have some DLL from third party that I need to license. It has some method that I must call from my own DLL. My DLL is referenced in couple of projects and I don't want to make changes to every hoster. Is there any method that I can use within my DLL which will call some method in my DLL? Like add some static class or constructor but without explicit call to that class from hosters? I am not sure if I am explaining it clearly. Please ask questions if needed.
ThirdPartyType license = new ThirdPartyType();
license.Load("license.xml");
This is a piece of licensing code that I want to place in my DLL and call it within the same DLL.
At the low level, the runtime supports "module initializers". However, C# does not provide any way of implementing them, so the closest you can manage is a static constructor ("type initializer") or just a regular constructor.
However, it is probably a bad idea to hook your licencing into either a module initializer or a type initializer, as you don't know when they will run, and it could impact code that wasn't going to access your lib. It is somewhat frowned upon to take someone's app down because your licensing code decided it was unhappy - especially if your library wasn't actively being invoked at the time.
As such: I suggest the most appropriate place to do this is in either a constructor, or a post-construction Initialize(...) method (with the tool refusing to work unless supplied with valid details).
Related
I'm working on a collection of code where there's most of the functionality in a PCL. I want to init members like
class CentralInPCL {
public static Func<string> DefaultPathProvider;
This needs to be assigned a lambda () => Path.GetTempFileName() from an assembly built for one of the platforms.
How do I reliably assign this lambda in another assembly?
Can I guarantee a static constructor of a helper class, in another assembly, will be run before any instances of CentralInPCL might be used?
I may have completely mis-understood something about how a PCL works but we're trying to avoid having user code have to pass parameters to the PCL.
As I understand them, a PCL is a leaf library called by platform-specific assemblies.
You would normally give it access to platform stuff by injecting an object or lambda, typically confirming to an interface defined in the PCL.
However, that injection process is explicit and has to be out there in some platform-specific code, usually user code.
I'm trying to add a bit more magic and have some defaults injected without the user knowing.
An old 2005 answer from Jon Skeet suggests you couldn't do it, at least back then.
I found a recipe for doing it with Fody, weaving in a Module Initializer which is an IL thing not able to be declared in C#.
Failing which, we need to require the user to include a call to setup static defaults somewhere.
I have a project where I want only one class to have access to a dll. I would be content with hiding the dll from intellisense, but still having access to it if that is an option. Either way, I want only one class to use the dll and for it not to be seen and/or accessible otherwise.
I'm using C# in visual studios.
Simply said: You can't do that (but keep reading).
Basically, a DLL (From the .NET perspective) is a bunch of code and config files. No more than that. So, given that you'll need to make public those classes in order to be used from another ones outside that assembly then you can not.
What you can do (I ended up doing this a few years ago) is to use some kind of reflection to determine which class (and namespace) is trying to access your assembly and only permit the proper one.
Other way is to implement a key negotiation between your DLL and the permitted assembly. You'll need to implement those manually, as far as I know.
Anyway, keep in mind there's always a way to bypass this kind of protection by disassembling and modifying your code. So, at least, don't forget to obfuscate the file. Anyway, this will just make it a little more painful, but still possible.
An alternate approach, if you goal is to stop people using the functionality of the dll by accident is to push your wrapper class into an intermediary assembly. Your project then references that intermediary project, rather than the underlying dll which effectively hides it. So your project structure would change to something like this:
Main Project -> references API Wrapper Project -> references API DLL
For this to work, your wrapper project needs to make sure that it doesn't accidentally expose any of the API DLL classes through its public interface.
Obviously this doesn't stop your developers from going in and adding a reference to the API DLL so that they can use the library directly, but if the goal is to stop accidental access to the API DLL classes because intellisense has helped the developer out a bit too much then it might be a viable option.
I am not even sure if this is possible so apologies if not. I have googled quite extensively and not found what I am looking for.
Basically we have an application produced by a third party, which, to be perfectly blunt is rubbish. We have a particular issue and have managed to trace the problem using ILSpy to a method within a DLL. Obviously we don't have (nor are able to get) the source code and the company in question is unwilling to fix the problem in any reasonable timescales.
So, we've investigated various avenues of investigation and come up with nothing. I've been looking into seeing whether this can be done using reflection and this is pretty much the last hope we have of getting this to work. In a nutshell, what I would like to do is the following:
Create a simple class library with the same name as the existing DLL
Use reflection to import the methods from the existing DLL
Somehow override the method in question with my own, correct code
Rebuild the code, so I have a new DLL, containing 99% of the functionality of the existing DLL but with my override code providing the correct functionality.
I have found, during my investigations TypeBuilder.DefineMethodOverride and also a page from StackOverflow, which seems similar but not quite what I am looking for.
http://msdn.microsoft.com/en-us/library/system.reflection.emit.typebuilder.definemethodoverride.aspx
Is there a way to "override" a method with reflection?
Any advice appreciated!
Andrew
Edit
The other possible idea I has was to produce a partial class containing the override function, but that didn't seem feasible either.
You can override the method only if it is virtual, and it doesn't matter whether you do it through reflection or statically. I would suggest using a decompiler (there are a lot of free ones available) and fixing the code in MSIL. Then you can generate a new assembly from the MSIL.
I think your first idea is good.
If the third party class isn't sealed, you can derive from it, and add your own method, with a different name, to correct the behavior that is wrong.
If you need it to be in 1 dll, you can use IlMerge.
If your third party class is sealed you can just have an instance of this third party class in your new class and call the methods when needed.
But you'll have to check that the method you want to "override" isn't called inside that library, because if it is this solution won't work...
It's not very clean, but it can be a temporary solution during the time the company that edits the library fixes the problem.
And when it's fixed you'd just have to rename the method you use, so it won't be time consuming.
From what you have described I would recommend modifying the original assembly. The process is essentially
Decompile the assembly into MSIL, C# or whatever language you so choose
Modify the decompiled assembly to include your changes
Recompile the assembly using the modified source
From what I can see Reflexil allows you to do just that, although it may require that you buy Resharper (I've not tried it myself)
Alternatively you can use ILDasm to decompile the entire assembly to a single file, modify the file and then recompile it using ILAsm
I know I'm coming in a bit late on this, but I'd agree with Charleh; if you've got a class that's not behaving well and isn't conducive to substitution, but at least declares its methods as virtual, then you're in luck. The following uses references to Castle.Core and Patterns:
var interceptor = new DelegateInterceptor(proceed: call =>
{
if(ShouldCallProceed(call)) call.Proceed();
else AlternativeLogic();
});
var generator = new ProxyGenerator();
var proxy = generator.CreateClassProxy<UncooperativeType>(interceptor);
proxy.RubbishMethod();
I've also taken the liberty of providing a running sample of this in LinqPad. It shows the difference between methods that allow interception (virtual ones) and ones that don't. It also shows a useful way of trapping exceptions without all the code using Try.Do from Patterns.
In C#, is it possible to restrict who can call a method at compile time?
I've looked into directives, but that didn't work since I can't assign values to symbols.
#define WHO VisualStudioUser.Current // does not work
I also looked into Code Access Security (CAS) but that's runtime enforcement, not compile time.
The requirement is to restrict access to a method at compile time for specific developers given the method exists in a pre-compiled assembly.
here's more details...
I'm building a framework or a series or assemblies for a team of developers. Because of our software license restrictions, I can only allow a few developers to write code to make a call to some restricted methods. The developers will not have access to the source code of the framework but they'll have access to the compiled framework assemblies.
The quick answer will be: No this isn't possible, and if you need to do it, you're Doing It Wrong.
How would this even work? Does it depend who who's running the code or who wrote it?
Edit There's kind of a way using InternalsVisibleTo and restricting accessing in source control to the assemblies that InternalsVisibleTo is specified for. See Jordão's answer
The requirement is to restrict access to a method at compile time for specific developers given the method exists in a pre-compiled assembly.
One way is to mark the method private or internal, it won't be callable by anyone outside the assembly. UPDATE: Also take a look at the InternalsVisibleTo attribute, which is used to define which assemblies can "see" internals of your assembly.
Another way is to divide the code you want to distribute from the code you don't want people to call into separate assemblies. Maybe you just share an assembly mostly of interfaces with your users, that they them compile against; and you have a separate assembly with implementations that they shouldn't reference directly. Your internal team would have access to the implementation assembly. This is just a common form of dependency management, the dependency inversion principle.
Draft:
Compile the restricted code into (obfuscated) DLLs: TypeA.dll, TypeB.dll etc.
Define an interface for each type, and compile them into separate DLLs: ITypeA.dll, ITypeB.dll etc.
Create a "guard assembly", and embed all restricted assemblies into it: Guard.dll. This has a ResolveEventHandler, and methods to instantiate different types defined in the embedded restricted DLLs. Instances are returned through their interface.
Developers get the interface DLLs and the Guard.dll. Each developer can get a Guard.dll with special authentication tokens in it. For example, a Guard.dll can be bound to PC, an IP address, a GUID issued to the developer, anything.
The developer can instantiate those types for which she has the proper authentication code, and uses the object instance through an interface.
Sorry this is a bit fuzzy, because it was more than a year ago when I used these techniques. I hope the main idea is clear.
Can you try using Extensible C# developed by ResolveCorp, some of the links for study and implementation are:
http://zef.me/782/extensible-c
http://www.codeproject.com/KB/architecture/DbCwithXCSharp.aspx
http://weblogs.asp.net/nunitaddin/archive/2003/02/14/2412.aspx
http://www.devx.com/dotnet/Article/11579/0/page/5
Greetings all,
I’m working on a C# program that requires being able to get the index of the hot item in Windows 7 Explorer’s new ItemsView control. Fortunately, Microsoft has provided a way to do this through UI Automation, by querying custom properties of the control.
Unfortunately, the System.Windows.Automation namespace inexplicably does not seem to provide a way to query custom properties! This leaves me with the undesirable position of having to completely ditch the C# Automation namespace and use only the unmanaged COM version. One way to do it would be to put all the Automation code in a separate C++/CLI module and call it from my C# application. However, I would like to avoid this option if possible, as it adds more files to my project, and I’d have to worry about 32/64-bit problems and such.
The other option is to make use of the ComImport attribute to declare the relevant interfaces and do everything through COM-interop. This is what I would like to do. However, the relevant interfaces, such as IUIAutomation and IUIAutomationElement, are FREAKING HUGE. They have hundreds of methods in total, and reference tons and tons of interfaces (which I assume I would have to also declare), almost all of which I will never ever use. I don’t think the UI Automation interfaces are declared in any Type Library either, so I can’t use TLBIMP.
Is there any way I can avoid having to manually translate a bajillion method signatures into C# and instead only declare the ten or so methods I actually need? I see that C# 4.0 added a new “dynamic” type that is supposed to ease COM interop; is that at all relevant to my problem?
Thanks
The most important thing (from the perspective of calling a COM method from C#) is that the methods appear in the interface in the right order. If you're not using a method, you can just declare it as void and nothing bad will happen (unless you actually call it!). This saves you from having to work out the correct signatures and define all the other types, etc. For example,
[ComImport, Guid("30cbe57d-d9d0-452a-ab13-7ac5ac4825ee"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IUIAutomation
{
void CompareElements();
void CompareRuntimeIds();
void GetRootElement();
// 50 or so other methods...
// ... define only the signatures for the ones you actually need
}
The methods should be defined in exactly the same order they appear in UIAutomationClient.h (in the Windows SDK).