Lingering assembly dependency in C# .NET - c#

My C# project - we'll call it the SuperUI - used to make use of a class from an external assembly. Now it doesn't, but the compiler won't let me build the project without the assembly reference in place. Let me elaborate.
This project used to throw and catch a custom exception class - the SuperException - which was derived from the standard System.Exception and lived in a separate, precompiled assembly, SuperAssembly.DLL, which I referenced.
Eventually, I decided this was a pointless exercise and replaced all SuperExceptions with a System.SuitableStandardException in each case. I removed the reference to SuperException.DLL, but am now met with the following on trying to compile the project:
The type 'SuperException' is defined in an assembly that is not referenced. You must add a reference to assembly 'SuperException, Version=1.1.0.0 (...)'
The source file referenced by the error doesn't seem relevant; it's the project namespace that gets highlighted in the IDE.
Now, here's the thing:
All uses of SuperException have been eliminated from the project's code.
Compared to another project that compiles fine without a reference to SuperException.DLL, I only reference one more assembly - and that references nothing that my project doesn't reference itself. While it's possible that any of these dependencies could throw SuperExceptions, I'm only catching the base Exception class and in any case... the other project builds fine!
I've done Visual Studio's "Clean Solution" and cleared everything out by hand, many times.
It's not the end of the world to include this reference, I just don't see why it's necessary any more. Nrrrgg. Any pointers welcome!


It's likely a transitive reference, where some type method call returns an instance of SuperException boxed ("downcast") as e.g. Exception, but from inspecting the code in the transitively included code, i.e. code from your external method calls, the compiler knows that you need to be able to have information about that type at some point.
Resharper would tell you where it's the case that you need to add a reference, and you could use Lütz Roeder's aka RedGate's Reflector to scan compiled IL for a reference to this type in two ways: 1) use the search-facility, 2) open each public type you're using and for that one which requires the "ghost" assembly, it will ask you to specify its location.
This most often happends to me when I reference Castle.Windsor but not Castle.MicroKernel. :p


Exit Visual Studio
Delete the bin and obj Folders in your solution directory
Restart and see what happens


I agree with the other comments here.. There is a reference, in plain text somewhere !
I have had similar problems in the past where searching through the project files returned nothing, turns out it was in some other file that wasn't automatically picked up in the search.
I don't think that creating a new project is the solution here.. You need to be positive that NONE of the references in your dependency tree use SuperException.. NONE
I have never experienced this to the point where I have needed to literally wipe the project, I have always found the reference somewhere. Ensure you are searching every file.
EDIT:
Just a point to add, if the location pointed to by the error seems random, that can often mean there is a mismatch between the compiled source and the source code file.. Is this a ASP.NET application? I have had it before where the compiled DLL's haven't been replaced on a rebuild in the ASP.NET temp folder causing things to get.. Interesting when debugging :)


I don't think this is a code issue. What I can see happening is that one of your existing references probably rely on that type in their own types which you are probably creating in your application.
If that is the case you do need that reference even if you don't explicitly use the type and even though the other referenced assembly has its own reference. You sometimes get that issue with 3rd party components which need references to types that you haven't referenced. The compiler is obviously seeing something in one of your existing referenced assemblies and is expecting you to referenced the dependent one.


Since it's a compiler error, there must be a reference or use of SuperException somewhere in the project.
Do a find/replace in the entire project or solution for that type and remove every reference (it's possible you already did this).
If you reference any types that inherits from SuperException (even if the type defined in another assembly), you need a reference to the assembly that SuperException is defined in.
Take the line that the compiler is showing the error on and start tracing the inheritance tree of the objects used on that line, you might find the source of it that way.


Thanks for your answers so far. I've tried every suggestion (except one) to no avail.
The suggestion I haven't tried is to create a new project and add all my stuff to it, the thought of which really tests my will to live. ;) I may try this tomorrow if I can be bothered. Thanks again.


There is really nothing very mysterious about VS projects nowadays - it's all text files, etc. SOMETHING must reference that class/dll, and that something must be part of your project.
Have you really grep'd or findstr'd the whole solution tree, every single file, for a reference to that exception?


This sounds pretty strange. Here's what I would check next:
Check that there's nothing lingering in your Properties/AssemblyInfo.cs file.
Check that there's nothing lingering in your SuperUI.csproj file.
Delete all references and re-add them.


Try creating a new project, and adding all your classes to it.


grep your project folder. It could be a hidden reference in your project, or a project that your project references. Cleanse with Notepad if needed.


If you reference any types that inherits from SuperException (even if the type defined in another assembly), you need a reference to the assembly that SuperException is defined in.
Seconded on that.
You might not be referencing SuperException, but you might be referencing SpecializedSuperException, which is derived from, or somehow otherwise uses SuperException - your grep of the project for SuperException won't be catching it though.
Try have a hack with the trial of NDepend


This is where tools like Resharper really pay off -- a simple Find Usages usually tells me of such "ghost dependencies" several times.
Maybe you could go to your definition of the SuperException class and try to Find All References(). You might also want to investigate if the assembly SuperException is has a circular dependency on your main assembly (e.g., main assembly depends on exception assembly depends on main assembly...).


I’ve had a very similar assembly reference issue that was happening when my C# library had a dependent C++/CLI assembly.
The problem that was I was inheriting a public class from that C++/CLI assembly in my C# assembly library. That meant that the inheritance chain was spanning across multiple assemblies.
I was hoping that any client would be smart enough to indirectly load the C++/CLI assembly any time the C# library needed it, but that was not the case even at compile time.
I got rid of this problem by breaking the inheritance between the classes that were spanning across those two assembly libraries and using aggregation instead.
My client was finally happy and did not require the C++/CLI assembly as a dependency anymore.
In your word you would probably have to make sure that SuitableStandardException does not inherit from SuperException in order to eliminate the SuperException.DLL as a reference.
Use encapsulation instead of inheritance and create a SuperException data member in your new SuitableStandardException.
If that does not solve it, you might have more classes spanning inheritance across some assemblies, in your case SuperAssembly.DLL and superException.dll.
If you can't find all of them try this trick:
Make all your public members and classes in SuperAssembly.DLL internal.
In the SuperAssembly.DLL make friends with SuperException.DLL:
[assembly:InternalsVisibleTo("SuperException, PublicKey=0024000004800000....)]
Make sure that they build and remove the SuperAssembly.DLL reference from any client that already references SuperException.DLL.


grep -R SuperException * in the base of your project (get grep from somewhere first) just to be sure.

Related

Reference has not compile-time usages

I've been watching over the architecture view of our solution created by ReSharper, when I noticed some of the project references has no compile-time usages, does that mean I can change assemblies at runtime?

In simple terms, no compile-time usage means that your code will compile even if you remove the reference. You cannot directly derive anything regarding runtime from this statement. It might even be that your application runs perfectly fine if you just remove this reference. It might also be that your reference is somewhat obfuscated and the compiler doesn't know it. This could be because the reference is implementing interfaces that you compile against or you are looking for it manually at runtime (see Florians answer). You could probably also hide it with reflection if you really wanted to. But that would also need to load the assembly manually at runtime.
At compile-time, the compiler will link the new binaries to the corresponding code in the referenced assemblies. This will allow automatically loading the assembly at runtime. It will also copy const values to your assembly.
You can definitely change the referenced assembly between compile- and runtime, although you should tread very carefully. If method signatures changed, compile-time references will break.
At runtime, referenced assemblies will be loaded once you try to interact with them. Once an assembly is loaded, it cannot be unloaded directly. You can only unload AppDomains. So if you want to change assemblies at runtime, look into AppDomains.
So what could be an intended use of those non-compile-time references? The most common architecture that uses this was mentioned by Florian in the other answer: Plugins. Also other dependencies where you want to separate your code from the actual implementation via interfaces. Your project references without compile-time dependencies are then only used to deliver the implementation to the actual application. Otherwise you would need to add this to your delivery and debugging process, which can be a pain depending on your project.

The type is defined in an assembly that is not referenced, how to find the cause?

I know the error message is common and there are plenty of questions on SO about this error, but no solutions have helped me so far, so I decided to ask the question. Difference to most of similar questions is me using App_Code directory.
Error message:
CS0012: The type 'Project.Rights.OperationsProvider' is defined in an
assembly that is not referenced. You must add a reference to assembly
'Project.Rights, version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Source File:
c:\inetpub\wwwroot\Test\Website\App_Code\Company\Project\BusinessLogic\Manager.cs
Following suggestions here and here, I have deleted all instances of Project.Rights.dll inside C:\Windows\Microsoft.NET/*.*
According to this, I checked if .cs files in question have build action set to "Compile". They do.
I have also double checked that the .cs file containing the "Project.Rights.OperationsProvider" type is deployed to App_Code directory.
For some reason, application is not looking for the type in the App_Code directory. Since I've deleted all instances of Project.Rights.dll (that I know of), I don't know which assembly the error message is mentioning.

When you get this error it isn't always obvious what is going on, but as the error says - you are missing a reference. Take the following line of code as an example:
MyObjectType a = new MyObjectType("parameter");
It looks simple enough and you probably have referenced "MyObjectType" correctly. But lets say one of the overloads for the "MyObjectType" constructor takes a type that you don't have referenced. For example there is an overload defined as:
public MyObjectType(TypeFromOtherAssembly parameter) {
// ... normal constructor code ...
}
That is at least one case where you will get this error. So, look for this type of pattern where you have referenced the type but not all the types of the properties or method parameters that are possible for functions being called on that type.
Hopefully this at least gets you going in the right direction!

Check target framework in the projects.
In my case "You must add a reference to assembly" actually meant, that caller and reference projects didn't have the same target framework. The caller project had .Net 4.5 , but referenced library had target 4.6.1.
I am sure, that MS compiler can be smarter and log more meaningful error message. I've added a suggestion to https://github.com/dotnet/roslyn/issues/14756

In my case this was because doing a NuGet package update had only updated references to a dll dependency in some but not all projects in my solution - resulting in conflicting versions. Using a grep-style tool to search text within *.csproj files in my solution it was then easy to see the projects that still needed to be updated.

When you get this error, it means that code you are using makes a reference to a type that is in an assembly, but the assembly is not part of your project so it can't use it.
Deleting Project.Rights.dll is the opposite of what you want. You need to make sure your project can reference the assembly. So it must either be placed in the Global Assembly Cache or your web application's ~/Bin directory.
Edit-If you don't want to use the assembly, then deleting it is not the proper solution either. Instead, you must remove all references to it in your code. Since the assembly isn't directly needed by code you've written, but instead by something else you're referencing, you'll have to replace that referenced assembly with something that doesn't have Project.Rights.dll as a dependency.

In my case, I was referencing a library that was being built to the wrong Platform/Configuration (I had just created the referenced library).
Furthermore, I was unable to fix the problem in Visual Studio Configuration Manager -- unable to switch and create new Platforms and Configurations for this library. I fixed it by correcting the entries in the ProjectConfigurationPlatforms section of the .sln file for that project. All its permutations were set to Debug|Any CPU (I'm not sure how I did that). I overwrote the entries for the broken project with the ones for a working project and changed the GUID for each entry.
Entries for functioning project
{9E93345C-7A51-4E9A-ACB0-DAAB8F1A1267}.Release|x64.ActiveCfg = Release|x64
{9E93345C-7A51-4E9A-ACB0-DAAB8F1A1267}.Release|x64.Build.0 = Release|x64
Entries for corrupted project
{94562215-903C-47F3-BF64-8B90EF43FD27}.Release|x64.ActiveCfg = Debug|Any CPU
{94562215-903C-47F3-BF64-8B90EF43FD27}.Release|x64.Build.0 = Debug|Any CPU
Corrupted entries now fixed
{94562215-903C-47F3-BF64-8B90EF43FD27}.Release|x64.ActiveCfg = Release|x64
{94562215-903C-47F3-BF64-8B90EF43FD27}.Release|x64.Build.0 = Release|x64
I hope this helps someone.

It just happened to me that different projects were referencing different copies of the same dll.
I made sure all referenced the same file on disk, and the error disappeared as I expected.

Unloading and reloading the class library in Visual Studio solved this for me.

For me, this was caused by the project both directly and indirectly (through another dependency) referencing two different builds of Bouncy Castle that had different assembly names. One of the Bouncy Castle builds was the NuGet package, the other one was a debug build of the source downloaded from GitHub. Both were nominally version 1.8.1, but the project settings of the GitHub code set the assembly name to BouncyCastle whereas the NuGet package had the assembly name BouncyCastle.Crypto. Changing the project settings, thus aligning the assembly names, fixed the problem.

It didn't work for me when I've tried to add the reference from the .NET Assemblies tab.
It worked, though, when I've added the reference with BROWSE to C:\Windows\Microsoft.NET\Framework\v4.0.30319

I had this issue on a newly created solution that used existing projects. For some reason, one project could not "see" one other project, even though it had the same reference as every other project, and the referenced project was also building. I suspect that it was failing to detect something having to do with multiple target frameworks, because it was building in one framework but not the other.
Cleaning and rebuilding didn't work, and restarting VS didn't work.
What ended up working was opening a "Developer Command Prompt for VS 2019" and then issuing a msbuild MySolution.sln command. This completed successfully, and afterwards VS started building successfully also.

one of main reason can be the property of DLL
you must before do any thing to check the specific version property if it true make it false
Reason:
maybe the source code joined with other (old)version when you build it , but this Library upgraded with new update the version now different in the Assembly Cash and your application forbidden to get new DLL ,and after disable specific version property your applacaten will be free to get the new version of DLL references

Maybe a library (DLL file) you are using requires another library. In my case, I referenced a library that contained a database entity model - but I forgot to reference the entity framework library.

This can also mean you use a library, which exposes (public) types that are defined in a library. Even when you do not use these specifically in your library (the one that doesn't build).
What this probably prevents is you writing code that uses a class (which in its signature has the types from a library not referenced) that you cannot use.

For me the reason why the error appeared was that the WebForm where the error was reported has been moved from another folder, but the name of its codefile class remained unchanged and didn't correspond to the actual path.
Initial state:
Original file path: /Folder1/Subfolder1/MyWebForm.aspx.cs
Original codefile class name: Folder1_Subfolder1_MyWebForm
After the file was moved:
File path: /Folder1/MyWebForm.aspx.cs
Codefile class name (unchanged, with the error shown): Folder1_Subfolder1_MyWebForm
The solution:
Rename your codefile class Folder1_Subfolder1_MyWebForm
to one corresponding with the new path: Folder1_MyWebForm
All at once - problem solved, no errors reporting..

The type 'Domain.tblUser' is defined in an assembly that is not
referenced. You must add a reference to assembly 'Domain,
Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
**Solved:**
Add reference of my domain library layer to my web app libary layer
Note: Make sure your references are correct according to you DI container

In my case this was because I used
Implicit Operator
between BLL and DAL classes.when I want to use BLL Layer In Application Layer I got this error.
I changed
implicit operator
to
explicit operator
it be OK.
Thanks

In my case the version of the dll referenced was actually newer than the one that I had before.
I just needed to roll back to the previous release and that fixed it.

I have a similar problem, and I remove the RuntimeFrameworkVersion, and the problem was fixed.
Try to remove 1.1.1 or

My problem was that the Output Type for one of my projects was set to Console Application. To fix this, I right-clicked the project, chose Properties, clicked the Application tab, and change Output Type (from Console Application) to Class Library. After I re-compiled, this error went away.

Clean your solution and rebuild worked for me (in Visual Studio, these are options you get when you right click in your solution explorer), the error is gone in my project.

Does a Visual Studio 2012 project use a reference DLL or local file first?

I may not be asking this question correctly as I haven't been able to find a reference here or on Google. I need to modify a class that is in one of my reference DLL's. Will VS look at the reference DLL first or the local file first ? It seems to look at the reference DLL first. Is there a way to tell VS which to look at first ?
Thanks
Clarification - I have a class definition in the reference DLL and also in a local project file. The local project file is the class definition that I need the program to use.

Using an alias on your references, you can specify which of two similarly named classes you are referring to in your code.
This is explained by Jon Skeet here:
What use is the Aliases property of assembly references in Visual Studio 8
Limitations
This will only help you, if you instanciate that class yourself. It is not possible to let a foreign assembly create instances of your own class if there is no dedicated mechanism (i.e. API) for doing so.

Your question is quite vague, but if you use the Fusion Log Viewer FusLogVw.exe (just search for it on your computer) you can see what dlls are loaded and which paths were used to look for it.

This depends on how you setup your reference to the project in question. Visual Studio has 2 concepts of references.
Project to Project
Project to DLL
For the sake of this discussion lets call the main project A and the referenced project B (the class to change is located in B)
If there is a project to project reference from A to B then the build is always against the latest source code. Hence if you change the class definition A will always build against the changed class.
If there is a project to DLL reference from A to B then things are a bit murkier. There are so many possibilities here that it is hard to speculate intelligently what will happen. It may get the updated class, it may not, it may after a second rebuild.
In general though if you have 2 projects in the same solution and one references the other you should always use a project to project reference. The easiest way to guarantee this is to delete the reference, right click select add reference and go through the project route instead of "Browse".

c# : Utility to find circular references / compile in correct order?

doers anyone know of a good utility or program to interrogate a solution or a directory for all projects and tell you where circular references are and possible compile in order..
I remember see one a while ago but i can't find it anywhere..

NDepend is an excellent tool that will do this and a lot more. Maybe it's overkill for what you want, but there's a trial version so have a look...

You could chase down the dependency tree via System.Reflection. As you build the tree, when adding a node, you would check to see if any parents of the node are the same project or assembly as the one you're adding. If true, throw an exception out to the user.
Throwing technical exceptions like this one are ok if your users will be people who know how assembly references and exceptions work - people like Developers :)

I know this is a late answer, but I found using GraemeF and tsilb's answers both showed no dependency between the two assemblies. It looks like if you reverse the order of dependencies (Assembly A references B, but you switch it to B referencing A), it leaves the dependency in the build order. To solve this, open the Properties dialog for your solution, go to Common Properties, and then Project Dependencies. Find the Assembly A and remove the dependency on Assembly B. This will allow you to add the reference normally.

If you use project references between the projects in your solution the correct build order will be determined automatically by Visual Studio (or MSBuild). This breaks of course if you use assembly references.. Also Visual Studio will stop you from adding circular project references.

I inherited a gigantic visual studio solution with a few circular reference paths. I wrote a linqpad script to help find the circular reference chain:
https://github.com/ronnieoverby/linqpad-utils/blob/master/Find%20circular%20references.linq
My implementation is probably naive, but it worked reasonably fast for me.

Can a referenced DLL be loaded even if it's not called?

Env.: .NET / VS2008
Hi All,
My app uses a 3rd party DLL assembly separately installed on some systems (clearly identified) but not all of them.
Which means that on some systems, the DLL is not there hence must not be called. To solve this, I have 2 versions of the app (using 2 configurations) for the 2 use cases. In one of them, all calls to the DLL are #if'ed out.
Since there are no calls to the DLL compiled at all in the app(they're #if'ed out), is it safe to assume that the app won't try to load the DLL even though it is referenced?
Or should I also exclude the reference?
Note: Asked in reaction to womp's comment in this question.
TIA,

IIRC, the C# compiler will omit references to dll's that are never actually used in the code. So if all code is inside #ifs, the reference to the dll will not be there in your compiled app, and the dll will never be loaded.
You can check this using Reflector, by the way. Just drag & drop your compiled app into Reflector, and look at the References node. ILDASM also provides this feature, I think.
Caveat: DllImports and dynamic type loading (e.g., Type.GetType("type,dll")) will dynamically load dlls without the C# compiler knowing or caring. But again, if inside the proper #ifs, nothing will be loaded.

I would exclude it. It might load it no matter what and if you have a type reference, then that also could cause a problem.

Why not load the the assembly dynamically if needed/available? And then if its gets added at a later date you can just make use of it? You'll only need one version of your app also.

You are safe with a reference but without the actual DLL if you never (obviously) instantiate and referenced class AND never refer to the Class in any instantiated or referenced object.
Typically your DLL will be loaded the first time the Class Constructor of a referenced Class is run.
HTH
Jan

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