I have an abstract class compiled into a DLL (let's call it BaseClass.dll) which serves as a base for other classes to inherit from. These other classes are also compiled into DLL's (let's call one of them InheritedClass.dll) which can be used as plugins for my main application which can call the same methods in each plugin as the abstract class forces them to implement.
However, there's some functionality which will be common to all the plugins and so I would prefer if I could implement those in the base class. This cuts down on redundancy and also eliminates the possibility of whoever writes the plugin to make mistakes when implementing that functionality.
One such example is a piece of code that requires the name of the compiled DLL file. A method that would've worked could look like this:
public string GetName()
{
return System.IO.Path.GetFileName(System.Reflection.Assembly.GetExecutingAssembly().CodeBase);
}
The problem is that GetExecutingAssembly() returns the assembly for the code that is currently running, not the assembly into which it has been compiled. So, if I put the above function in BaseClass, it returns (BaseClass.cs), regardless of the name of the DLL that it is compiled into. This means that I have to put it in InheritedClass and can't put it in BaseClass. As explained above, I'd like to avoid that as I don't want to labour the developer of the plugins with this bit of common code and I don't want to rely on these third party developers to get it right.
Is this even possible? Is there a way I can get the name of the DLL which inherited from this base class through code that sits in the base class?
GetType always returns the actual type of an object, so you can use that to find out what type you actually are, then chase from there to the assembly:
public string GetName()
{
return System.IO.Path.GetFileName(GetType().Assembly.CodeBase);
}
Hopefully you'll come up with a better name for this method later. GetName is horribly vague.
Related
Is there and easy way to decompile a C# DLL (like ILSpy does, for example), but instead of method bodies, have the methods return default values (or throw runtime exceptions for that matter)?
Why do I need this? I am trying to replace some classes in a .dll library. I can't decompile the entire library, since it contains many lambda function and iterators that cause problems when decompiled.
I had, however, success doing this: Copy the decompiled source of the class I want to change, paste it into a new project and include the original .dll as a library. Then, change the class to my liking (change methods implementation for now), and then compile the project and inject the compiled IL code into the original .dll via a disassembler.
This has worked out so far with a success, however now I have run into a problem. The class (let's say A) that I'm trying to change now, passes this as an argument to other classes (let's say B), and it's generating a compile error (since the original B class expects the original A class, and not the "fake" A class that I'm editing).
This, of course, would not be a problem if I had the complete source code to the .dll library, but I don't. Fortunately, I don't have to. If I had a "structure-only" source code (declarations of classes, fields, methods, interfaces and what not, but no method implemetations), I could copy-paste the source of class A into this sructure-only sorce code, make the changes I need, compile, and then inject the IL code as before.
So, can I easily get the sructure-only sorce code (again, method implementation can be eighter returning default value, or throwing runtime exception), or is there a better to replace a class in a .dll library like that?
We have code that is called by an external framework, ARDEN. Short of a comment (easily overlooked), how can I effectively notify developers of tie in's to this framework? Specifically, a tie in couples the CLASS, NAMESPACE and METHOD to said framework.
namespace MyCompany//changing namespace for this class is NOT SAFE
{
public class MyClass//changing class name is NOT SAFE
{
[TiedToArdenAttribute]//maybe an attribute?
public void MethodCalledByArden() {}//adding params, changing name is NOT SAFE
public void NotCalledByArden() {}//changing this method signature, name, params is OK
}
}
Under normal circumstances, for example when I change the name of MyClass in an assembly via visual studio I can't compile without fixing the references to said class. If the namespace, classname or method name changes...there should be a warning that says "best fix Arden to deal with this change". I considered an Error, but since there's no way to verify Arden is fixed I don't believe that will work.
Is there a way to achieve a similar result for this external framework?
I think whatever you do can be undone by other developers - they can rename class, remove comments, remove attributes.
Try to move this class to separate library instead. And in your project add reference to compiled assembly. That will make class name fixed in your project.
If others are using the code, it is best to talk in terms of contracts and not class instances via interfaces. By allowing the consumer to use an Interface will dictate the primary changes such as property changes...but things like internal class name changes will not affect a consumer. Plus you can version your classes, while working on a new class, the old class could still be used by the consumer until the factory internally releases it, without the consumer knowing that V2 of the class is being used.
Is there any way to save an entire class definition for a C# object to a file / data store?
I use the [Serializable] tag and ISerializable interface to do this already, but both of these rely on the object definition being in the assembly at run time.
What I'm looking for is a solution to the following scenario:
1) User creates object MyClass in my software and saves it
For the purpose of this example, MyClass is a stand-alone object that doesn't rely on any other class in the system:
i.e. this could be the entire definition:
public class MyClass
{
public int MyProperty { get; set; }
public void DoSomething() { /* do something, like Console.Write(""); */ }
}
2) We release a patch that removes MyClass from the system
3) User loads the saved MyClass from step 1 and calls DoSomething() on it - and has the function work exactly the same as it did before the patch removed the class from the system
Is there any way this can be done without reflection / emit trickery?
No, this won't work without emitting the type definition. What you are trying to do is actually save off the code (otherwise, how would DoSomething work?) - which is what the compiler does for you. Plain serialization will never work for you here.
So, if you need to save behavior as well as state, you need to either keep the historical code around, use some type of reflection emit trickery to persist the type definition as a loadable assembly, or use dynamic programming tricks that treat data as executable code.
When I have had do versioned serialization before, I normally have custom serialization logic and a "version" attribute on the object - using this I can create a type that I've moved and renamed - say SomeClass to Archive.SomeClassV3. You can use Version Tolerant Serialization for this, but I prefer to implement ISerializable and use serialization proxies if this is required. (Well, actually I prefer to avoid this problem altogether!)
Well, you could keep all of these serializable classes in their own DLLs, package the DLLs with the application, and have the DLLs loaded at runtime. That way, even if you remove the classes from the latest version of the application, the loaded DLLs will still work.
This seems like a scary approach, though ... now you have clients running ancient code that you no longer even have in your source control repository. How are you supposed to debug that?
You talking about not class-property serialization, but about process-serialization (or method-, doesn't matter). But unlike property serialization, this should contain MSIL-code that runs when you need it. So you must somehow translate it to a bin-code and then run by Assembly.Load, for example. I guess this is not an easy way to do this. So, if this is possible - store your implementation of MyClass to a separate dll, or as a string (in c# language) for further compilation and execution by reflection.
I have the following situation:
A project MyCompany.MyProject.Domain which contains my domain model, and partial classes (such as Contact).
I want to 'extend' (by partial class, not extension method) my Contact class with a property Slug which will give me a simple URL friendly text representation of first and last name.
I have a string extension method ToSlug() in my Utility project MyCompany.MyProject.Utilities which does exactly what I want in 2).
The problem: My Utility project is already referencing my Domain project which means that I can't get the Domain project to see the Utility project's ToSlug() method without causing circular reference.
I'm not keen on creating another project to solve this, and I really want to keep the Slug logic shared.
How can I solve this?
Your Utility project referencing your MyCompany.MyProject.Domain seems like a bit of a code smell. I'm assuming here that these are utilities that specifically work on domain objects--if that's the case, then why don't you include MyCompany.MyProject.Utilities within your Domain project (naturally, modifying the namespace accordingly)?
In any case, the normal way to break these kinds of dependencies is to abstract what is required by one project into a set of interfaces, and encapsulate those in a separate assembly. Before doing that though, make sure that what you're doing conceptually is the right thing.
In your particular situation though, consider introducing an interface, viz., INameHolder:
public interface INameHolder
{
string FirstName { get; set; }
string LastName { get; set; }
}
Then Contact implements INameHolder. INameHolder exists in another assembly, let's call it MyCompany.MyProject.Domain.Interfaces.
Then your Utilities project references Interfaces (not Domain) and so does Domain, but Interfaces doesn't reference anything--the circular reference is broken.
copy ToSlug method to Domain project and Delegate Utility's ToSlug call to this new method
If you cannot share the domain (probably right) and it must consume the logic from a shared library then then you really have to introduce a another assembly.
Or you could load the logic at runtime in the domain by reflection in the domain to access the dependent library. Its not hard just breaks compile time checking.
If you're sure about keeping the code in the utility DLL (Eric's answer seems smart to me), then you could create an interface in your utility project, pass that interface as a parameter to your ToSlug method and then have your domain object implement the interface.
I'm working with a 3rd party c# class that has lots of great methods and properties - but as time has gone by I need to extend that class with methods and properties of my own. If it was my code I would just use that class as my base class and add my own properties and method on top - but this class has an internal constructor. (In my opinion it was short sited to make the constructor internal in the first place - why limit the ability to subclass?)
The only thing I could think of was to create method / properties on my class that simply called into theirs - but it's acres of code and, well, it just doesn't "feel" right.
Is there any way to use this class a base class?
You ask: "Why limit the ability to subclass?"
Because designing for inheritance is tricky, particularly if you're designing for other developers to inherit from your class. As Josh Bloch says in Effective Java, you should design for inheritance or prohibit it. In my view, unless you have a good reason to design for inheritance, you shouldn't do so speculatively.
Does the class implement an interface which you could also implement (possibly by proxying most calls back to an instance of the original)? There's often no really elegant answer here - and the best solution will depend on the exact situation, including what you're trying to add to the class.
If you're not adding any more state - just convenience methods, effectively - then extension methods may work well for you. But they don't change what data an object is capable of storing, so if you need to add your own specialised data, that won't work.
Sounds like a perfect application for extension methods:
MSDN extension method docs
"Extension methods enable you to "add" methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. Extension methods are a special kind of static method, but they are called as if they were instance methods on the extended type. For client code written in C# and Visual Basic, there is no apparent difference between calling an extension method and the methods that are actually defined in a type."
If the class has an internal constructor, and there are no public constructors, then that suggests that the designers did not intend for it to be subclassed. In that case, you can use encapsulation, or you can use extension methods.
Only if your class lives in the same assembly as the class you want to inherit from. An internal constructor limits the concrete implementations of the abstract class to the assembly defining the class. A class containing an internal constructor cannot be instantiated outside of the assembly.
Resharper has a nice feature to create delegating members.
Here is a sample of what you can do with it. It takes a couple of seconds.
I will not discuss whether you can build your own Facade around that 3rd party class. Previous authors are right, the library could be designed in the way that will not allow this. Suppose they have some coupled classes that have singletons that should be initialized in specific order or something like this - there may be a lot of design mistakes (or features) that 3rd party developers never care about, because they do not suppose that you will use their library in that way.
But OK, lets suppose that building a facade is not an impossible task, and you have in fact only one problem - there are too many methods you have to write wrappers around, and it is not good to do this manually.
I see 3 solutions to address exactly that problem
1) I suppose that new "dynamic" types of .NET 4.0 will allow you to workaround that problem without having to write "acres of code"
You should incapsulate an instance of 3rd party class into your class as a privare member with dynamic keyword
Your class should be derived from Dynamic or implement IDynamicObject interface. You will have to implement GetMember/SetMember functions that will forward all calls to the encapsulated instance of 3rd party class
Well, c# 4.0 is a future, Let's see on other solutions:
2) Do not write code manually if you have significant number of public methods (say more then 100). I would write a little console app that uses reflection and finds all public members and then automatically generates code to call encapsulated instance. For example
public type MethodName(params)
{
this.anInstanceOf3rdPartyClass.MethodName(params);
}
3) You can do the same as 2, but with the help of existing reflection tools, for example RedGate .NET Reflector. It will help you to list all classes and methods signatures. Then, paste all this in Word and a simple VB macro will let you generate the same code as you could do in 2.
Remark: As soon as you are not copying the code, but only copying method signatures, that are publicly available, I don't think you will violate the license agreement, but anyway it worth to re-check