The name of one of my classes was changed and I can't change it back. I have to mantain backwards compatibility and I don't want to write an wrapper with the old name.
Is there any easy way to give a class 2 names or to give it an alias?
Lifted from a comment by the OP:
Don't tell me to use the using directive since it must be done in the consumer side, and I don't want to change the projects that are using my library.
Arguably, your best option is to use a refactoring tool (like Resharper) to help you automate the conversion from the old name to the new name. However, if this is untenable to you for some reason, here are some alternatives:
If the types are in different assemblies you may be able to use a Type Forwarder. These allow you to redirect all references for a given type to an assembly ... but if IIRC, they can also redirect them to a new name as well.
Otherwise, within a single .cs source file you can apply a using statement:
using OldClassName = SomeNameSpace.NewClassName
This doesn't solve the problem globally, however, as it may become painful to change many .cs files to include this using statement.
Another alternative, may be to create a sub-class of the new type and name it the old name:
public class OldClassName : NewClassName
This gives you aliasing for the new class, but will require that you create duplicate public constructors and proxy static method calls to the renamed type. This is far from ideal ... and I generally don't recommend this.
Unfortunately, as the library author, the only way is X inherits Y, which has certain caveats.
It's possible but unlikely you could cheat with IL assembly.
Related
I'd like to use C#'s reflection and custom attributes to simplify registering a series of types with a central management class (i.e. it provides static methods taking a string key and invoking/retrieving the proper method/parameter for the associated type). Looking at other questions here and a couple places elsewhere, it seems like the best way of doing so is to simply iterate through all public types of the assembly -- since it's intended to be a library -- and check if each type has the proper attribute before adding the relevant values to the underlying Dictionaries. The reflection and iteration will definitely be slow, but I can live with it since it should only occur once.
Unfortunately, I can't figure out how to get an attribute from a type. For methods and assemblies, I can use CustomAttributeExtensions.GetCustomAttribute<MyAttribute>(base) from System.Reflection.Extensions, but that doesn't provide an overload for Type; the same for Assembly.GetCustomAttribute(Assembly, Type) and the .IsDefined(...) methods used in this question. Other suggestions use methods on the Type itself that, from the documentation, seem to be loaded from mscorelib.dll, but it didn't seem to be showing up in Intellisense even after adding the reference and I'm not sure how that .dll interacts with .NET Standard, anyway (as in, does it reduce the ability to run on arbitrary platforms at all?)
Am I missing something obvious, or is it really this hard to get an Attribute back off of a Type?
Try typeof(YourType).GetTypeInfo().GetCustomAttributes();
I have a set of strings like this:
System.Int32
string
bool[]
List<MyType.MyNestedType>
Dictionary<MyType.MyEnum, List<object>>
I would like to test if those strings are actually source code representations of valid types.
I'm in an environment, that doesn't support Roslyn and incorporating any sort of parser would be difficult. This is why I've tried using System.Type.GetType(string) to figure this out.
However, I'm going down a dirty road, because there are so many edge cases, where I need to modify the input string to represent an AssemblyQualifiedString. E.g. nested type "MyType.MyNestedType" needs to be "MyType+MyNestedType" and generics also have to be figured out the hard way.
Is there any helper method which does this kind of checking in .Net 2.0? I'm working in the Unity game engine, and we don't have any means to switch our system to a more sophisticated environment with available parsers.
Clarification
My company has developed a code generation system in Unity, which is not easily changed at this point. The one thing I need to add to it, is the ability to get a list of fields defined in a class (via reflection) and then separate them based on whether they are part of the default runtime assembly or if they are enclosed within #if UNITY_EDITOR preprocessor directives. When those are set, I basically want to handle those fields differently, but reflection alone can't tell me. Therefore I have decided to open my script files, look through the text for such define regions and then check if a field is declared within in them, and if true, put it in a separate FieldInfo[] array.
The one thing fixed and not changeable: All script will be inspected via reflection and a collection of FieldInfo is used to generate new source code elsewhere. I just need to separate that collection into individual ones for runtime vs editor assembly.
Custom types and nested generics are probably the hard part.
Can't you just have a "equivalency map to fully qualified name" or a few translation rules for all custom types ?
I guess you know by advance what you will encounter.
Or maybe run it on opposite way : at startup, scan your assembly(s) and for each class contained inside, generates the equivalent name "as it's supposed to appear" in your input file from the fully qualified name in GetType() format ?
For custom types of other assemblies, please note that you have to do things such as calling Assembly.LoadFile() or pass assembly name in second parameter to GetType() before to be able to load them.
See here for example : Resolve Type from Class Name in a Different Assembly
Maybe this answer could also help : How to parse C# generic type names?
Could you please detail what is the final purpose of project ? The problem is a bit surprising, especially for a unity project. Is it because you used some kind of weird serialization to persist state of some of your objects ?
This answer is more a few recommandations and questions to help you to clarify the needs than a definitive answer, but it can't hold in a single comment, and I think it provide useful informations
I need to use a iOS build setting in Unity3d that strips unused classes from bytecode but as it uses static analysis to discover which to remove- so any classes resolved through reflection will not be excluded from removal unless explicitly added to an exclusion list. I managed to remove all uses of reflection in my own code, but Mono itself seems to use a reflection based configuration to do a bunch of stuff and I've already added about a dozen classes to the exclusion list but now I'm to the point where exceptions are not giving any clues as to what class needs to be excluded for them to work.
My question is, is it possible to get a precise list of all the classes (with source assembly and namespace) resolved through reflection throughout every assembly that the application uses, and how would you go about it? I have Visual Studio 2012 and while I know it has powerful debugging tools I don't know how I would use them to this end.
Thanks.
The short version
You can't as there is no way to find all lookups via reflection using static analysis.
The long version
Just think of the following example: I write code that selects a class depending on user input, e.g. in pseudo code:
string action = ... ; // get some user input here, e.g. "Fire"
string clazz = "Do" + action;
var obj = Activator.CreateInstance("MyActions", clazz);
As you can see the actual full class name is not occuring anywhere in the code. So you would need to execute the code in every possible way to find out which values the clazz variable could assume. Therefore you cannot find out which classes this code would access via reflection.
Further Questions
What exact API from Mono are you using and what kind of exceptions are you getting? Maybe there is some alternative that could be used for your purpose.
At all the companies I have worked at I end up championing a core set of libraries that do nothing more than enhance and extend the .net libraries. Usually I have the namespaces such that they start with our company name but the sub namespaces mirror those of the System namespace.
Foo.IO;
Foo.Web
What I plan to do is take this one step further and replace the company namespace with the system namespace so that you only have to have the one using statement and thus have a better enhancement to the core library.
namespace System.IO
{
public static class StreamExtensions
{
...
}
}
The actual question
Now I know that this is possible, Microsoft do it in their own libraries and I have seen it done in other third party libraries but what I want to know is what, if any, are the long term implications of doing this such as a class name conflict in later versions of .net? Has anyone done this and had to handle a complication that has broken the simplicity of just being able to add an assembly reference?
UPDATE
Unfortunately this has turned into more of a debate of whether you should or should not do this which probably belongs over on Programmers. Indecently there is another SO question which does ask this but that was not the point of the question.
I wanted to know if there is a scenario that would crop up further down the road that would cause compilation errors or a strange behavior. The only two arguments that have come up is.
Microsoft adds a method to an object that matches the signature of extension method in the library but this is a mute point as it would make no difference to what namespace the extension method lives in as the implementation on the object would take precedence.
Someone else does the same thing in their third party library and we have a name clash. This is more likely and something we already have to deal with where third party libraries ILMerge other libraries into their assembly.
Just to be clear this is a stand alone library, it is for in house use, not to be made available externally and is there to extend the existing System libraries through Extension methods.
I would suggest do not do this. System namespace is .NET Framework namespace, if you want to customize classes from that namespace, make it explicit in your code.
That means make the customized class part of you custom namespace.
Do not mess up the things.
This may be a little off-topic, but in reference to the alternative approach you mention:
Usually I have the namespaces such that they start with our company name but the sub namespaces mirror those of the System namespace.
I've had some issues with that approach.
My company name is Resolv - as such, a lot of the stuff I write ends up going into a namespace in the form of Resolv.<ProjectName> (the rest will be <ClientName>.<ProjectName>).
I started building my library of extension methods, static classes and so-on in a namespace called Resolv.System
However, that created namespace resolution issues when using "fully qualified" type names that start with System (e.g. var myVar = new System.Collections.List<int>();).
While I would never use a fully qualified name in that particular case, it's something I do on occasion if the type I'm referencing is the only one from that namespace in the entire code file (in which case adding a using isn't warranted) - or on those occasions when two namespaces imported (with using statements) contain conflicting type names. Automated code generation tools (like resharper) often add those sort of references when there isn't an appropriate using statement too.
If I'm working on code within some namespace anywhere inside Resolv (e.g. Resolv.MyInternalProject) - and I put in what should be a fully qualified name - confusion ensues because of the Resolv.System namespace. The compiler walks back up the current namespace, gets to Resolv and then finds Resolv.System. That means - for example - that new System.Collections.List<int>() will attempt to use the non-existent class Resolv.System.Collections.List<int>().
Of course, I can get around that by using the form var myVar = new global::System.Collections.List<int>() but that's ugly and sort of a pain).
I've opted instead to include a "project name" in my extensions namespace tree, so now instead of Resolv.System I have Resolv.Extensions.System. From there the child namespaces mirror the System namespace (e.g. Resolv.Extensions.System.IO). That way I can have better control over whether I want to have System.xxx.xxxx references refer to my extensions, or the .net ones from any given code file (and it's only one using statement to add to my code files when I want to "turn on extensions").
Of course, I'll still have the System.xxx.xxx namespace confusion when working on code inside the Resolv.Extensions namespace - but that won't bug me on a daily basis! :)
What I plan to do is take this one step further and replace the
company namespace with the system namespace so that you only have to
have the one using statement and thus have a better enhancement to the
core library.
I don't understand how this will enchance the core library. What happens when Microsoft adds the same method to the String class and it does something entirely different? This is the reason they should be in their own namespace.
Now I know that this is possible, Microsoft do it in their own
libraries and I have seen it done in other third party libraries but
what I want to know is what, if any, are the long term implications of
doing this such as a class name conflict in later versions of .net?
The long term implications is if Microsoft adds the same method to a class as the extension method you create.
Has anyone done this and had to handle a complication that has broken
the simplicity of just being able to add an assembly reference?
I don't understand the reason you want to reduce the amount of references. You gain nothing by doing this, having utility methods in their own namespace and class is a valid design decision, people assume they will be seperate and not part of a Microsoft namespace.
It is a valid statement but the question about what are the
implications. Other people, including myself, have shied away from
doing this because of a "gut" feeling about messing with someone
else's namespace but no one has said do not do it because of this. If
you have a specific factual reason I would love to hear it.
The implication is a developers assumptions that the System namespace is filled with only Microsoft code.
Question in the title.
I'd like to avoid recompiling since the source code I'm modifying is third party and I'd like to use the original binaries where possible, and replace only the assembly which contains the class I modified. But I'm not sure if this is a safe thing to do. In C++ for example this is definitely a bad idea.
No.
The assemblies that reference your library refer to methods and types using (some form of) name, so as long as you don't change the names of public types and methods (used by other assemblies), you don't need to recompile any of the assemblies - they will work with the updated version of the library.
In most cases Tomas answer is correct, but there are some cases where it is not true:
When using strong naming (signing) change of a single character leads to a new signature, thous leading to a new strong name.
Setting in your project references for your assembly the property Specific Version to true and changing the version number manually or automatically in AssemblyInfo.cs
No. All other assemblies will automatically work with the newly updated library.