References from class library are not copied to running project bin folder

References from class library are not copied to running project bin folder - c#

I have a class library that represents my logic layer. To that library I've added a nuget package for Google.Apis.Analytics.v3 - it installed the package and all it's dependencies.
I have a console application that uses that logic class library (regular reference). everything is written and compiled fine.
The problem is that during runtime it threw an exception that Google.Apis.dll wasn't found. This DLL is a dependency that was downloaded with the nuget.
Checking the BIN folders, I've found that in the class library bin folder this DLL was present, but in the console application BIN folder it wasn't (while other related DLLs were). So this means that the not all references where copied during compilation.
I've searched online, and found all kind of workarounds that didn't really work (like manually editing the project file and removing a true xml line on that dll definition).
What I ended up doing is adding the same nuget library to my console application - it works but feels a little dirty and not the way it should be. I think the console app is the client who's supposed to get it's services from that logic class library which should know it's stuff without the "client" worrying about it.
Also, that console app is not the only one who's gonna use that service, I'm also planning on a web app that will use that functionality - so I will need to add the same nuget to that web app as well - again, feels a little messy...
Is it just me? is that the right way to go about it? I was thinking about writing a WCF project to handle that functionality - but that seems a little of a overhead for just on functionality, and probably slow my workflow down just to keep things "cleaner" in my opinion.
Am I just over-thinking it?
Thank

Explanation
For a sample scenario let's say we have project X, assembly A, and assembly B. Assembly A references assembly B, so project X includes a reference to both A and B. Also, project X includes code that references assembly A (e.g. A.SomeFunction()). Now, you create a new project Y which references project X.
So the dependency chain looks like this: Y => X => A => B
Visual Studio / MSBuild tries to be smart and only bring references over into project Y that it detects as being required by project X; it does this to avoid reference pollution in project Y. The problem is, since project X doesn't actually contain any code that explicitly uses assembly B (e.g. B.SomeFunction()), VS/MSBuild doesn't detect that B is required by X, and thus doesn't copy it over into project Y's bin directory; it only copies the X and A assemblies.
Solution
You have two options to solve this problem, both of which will result in assembly B being copied to project Y's bin directory:
Add a reference to assembly B in project Y.
Add dummy code to a file in project X that uses assembly B.
Personally I prefer option 2 for a couple reasons.
If you add another project in the future that references project X, you won't have to remember to also include a reference to assembly B (like you would have to do with option 1).
You can have explicit comments saying why the dummy code needs to be there and not to remove it. So if somebody does delete the code by accident (say with a refactor tool that looks for unused code), you can easily see from source control that the code is required and to restore it. If you use option 1 and somebody uses a refactor tool to clean up unused references, you don't have any comments; you will just see that a reference was removed from the .csproj file.
Here is a sample of the "dummy code" that I typically add when I encounter this situation.
// DO NOT DELETE THIS CODE UNLESS WE NO LONGER REQUIRE ASSEMBLY A!!!
private void DummyFunctionToMakeSureReferencesGetCopiedProperly_DO_NOT_DELETE_THIS_CODE()
{
// Assembly A is used by this file, and that assembly depends on assembly B,
// but this project does not have any code that explicitly references assembly B. Therefore, when another project references
// this project, this project's assembly and the assembly A get copied to the project's bin directory, but not
// assembly B. So in order to get the required assembly B copied over, we add some dummy code here (that never
// gets called) that references assembly B; this will flag VS/MSBuild to copy the required assembly B over as well.
var dummyType = typeof(B.SomeClass);
Console.WriteLine(dummyType.FullName);
}

If you have the following dependency chain:
Lib1 <-- Lib2 <-- MyApp
TLDR version: by not making assumptions, the build system avoids introducing uncertainty/unexpected behavior.
When you build MyApp, Lib2 will get copied to MyApp's bin directory for you, but Lib1 will not. You will need to add a reference to Lib2 and Lib1 in MyApp in order to get Lib1's dlls in MyApp's bin directory (otherwise you'll get the runtime error). It would be impossible (or maybe just really difficult) to identify the exact set of files that end up in Lib2's bin directory that would be safe & appropriate to copy over to MyApp's. If the build system made assumptions that everything in Lib2's bin directory was safe for MyApp, or if it implicitly referenced Lib1 for you, it could change the behavior of MyApp unintentionally.
Imagine a solution where more than 1 project depends on Lib2 but one of those projects wants to load an adjacent .dll file using Assembly.LoadFrom/Activator.CreateInstance/MEF/etc. (a plugin) and the other one does not. An automatic copy operation could grab Lib2 along with the plugin dll and copy it over to the first and the second project's build directory (since it's in the Lib2's bin directory as a result of a build operation). This would change the behavior of the second app.
Alternatively, if it was a little smarter and implicitly referenced Lib1 for you when you referenced Lib2 (and didn't just copy bin directory contents), it could still cause unintended consequences. What if MyApp already depended on Lib1, but it was using a GAC'd/ngen'd copy that was compatible with the one that Lib2 requires. If adding a reference to Lib2 implicitly created a reference to Lib1 for you, that could change which Lib1 got loaded and change the runtime behavior of your application. It could maybe detect that there already is a Lib1 in MyApp's bin directory and skip it, but then it would be making assumptions that the Lib1 that's already there is the right one. Maybe it's a stale .dll waiting to get wiped away by a Clean operation and the overwrite was the right move.
NuGet addresses the problem you're describing with package dependencies. If Lib1 and Lib2 both had nuget packages and the Lib2 package depended on the Lib1 package, when you add Lib2 to MyApp, Lib1 would get added as well. Both pacakges' dlls would end up in MyApp's bin directory.
The best thing to do is invert your thinking a little bit. Instead of thinking:
Lib2 needs a reference to Lib1 in order to compile so I'll add a reference to Lib1
Think:
MyApp needs Lib2. Whatever Lib2 needs, I need. So MyApp & Lib2 both get a reference to Lib1.

If you have 10's of dlls it's easier to do a copy with a postbuild event:
xcopy "$(ProjectDir)bin\*.dll" $(SolutionDir)MyTargetProject\bin\" /y

Related

What is the point of references in Visual Studio?

Kind of silly question, but I still can't understand it.
Let's assume I have A.exe file and B.dll file.
B.dll is located in ../Somewhere/Debug/B.dll.
I make a reference to this .dll from my A.exe project, but when I execute the A.exe it looks for the B.dll in the same directory, where A.exe is located. So why do I have to specify the path to B.dll (../Somewhere/Debug/B.dll) in my A.exe project if it does not actually use that?
I can build A.exe which references ../Somewhere/Debug/B.dll with CopyLocal = true. Then, I can make changes to the B.dll (for example add a new Class) and build it. After that I am able to use that new Class in my A.exe project, but if I set CopyLocal on B.dll reference to false and build A.exe, I will face the TypeLoadException once I try to execute A.exe, since it uses the old version of B.dll which is located in the same folder where A.exe is located.
The same thing with strongly named assemblies which are located in the GAC. I reference this assembly (e.g. ../Test/My.dll), but CLR still uses those which are located in the GAC.
Do references in Visual Studio play any role or they just serve for development purposes (like IntelliSense)?

References to assemblies (aka DLLs or EXEs) are used in two ways. Let's take your example. In B.dll, we have a class named ClassB which has a public default constructor and a public method (ClassB.MethodB) which takes a string and has a void return type.
In A.exe, the code instantiates an instance of a ClassB and calls MethodB on that instance:
var b = new ClassB();
b.MethodB("SomeString");
At compile time, the compiler needs to know about the existence of ClassB, as well as what its public methods/properties/etc. are. In C++, that would be encoded in an H file. In COM, it would be in a type library. In .NET languages (VB, C#, etc.), that is exposed as metadata in the assembly itself.
So, when you compile the A project into A.exe, you need to provide the compiler with a reference to the B.dll assembly; that's how the compiler knows what a B is. Note that there is nothing Visual Studio-specific in this; if you were to do this with csc.exe (the C# compiler), you'd still need to include the reference on the command line.
But, in addition to this, when A.exe runs, the runtime needs to load and JIT the B.dll assembly so that when the b.MethodB("SomeString"); line of code in A.exe runs, it can call the right method in B.dll. (JIT means just-in-time compile -- which really isn't pertinent here)
As #waleedNaveed points out, the runtime behavior is different if the assembly is strongly named or not. In particular, the runtime assembly search path for strongly-named assemblies starts with the GAC.
For non-strongly-named assemblies, the easiest place to find a referenced assembly is in the same folder as the currently executed assembly. That's why you typically set "copy local" to true; it makes it just work.

To answer your confusion regarding GAC. .NET framework starts by searching the dll(assembly) in the GAC (obviously if it is strongly named). If assembly is not found in the GAC, and if there is a .config file, then .NET framework searches the location in the configuration file, else .NET framework searches the assembly in the directory containing the executable (.exe). Even if the assembly is not found in the executable directory, then it gives the error.
Hope that answers your question and clears you confusion.

The compiler will copy B.dll every time you compile your solution.
The objective is to allow you to target a dll somewhere outside of your solution. As an example, this dll can be maintained by another team. (but in this case, an internal nuGet package would be a better solution.)
Note that referencing dlls in your compilation folder is not a good idea, because the content of this folder can be cleaned between compilation. In that case you use a source control for your referenced dlls, the read-only flag on the dll in this folder can cause compilation issues.

VS solution's props and target setting not copying files to output directory [duplicate]

I have a visual studio solution.
I have many projects in the solution.
There is one main project which acts as the start up and uses other projects.
There is one project say "ProjectX". Its reference is added to main project.
The ProjectX references another .NET dll (say abc.dll) that isn't part of the solution.
Now this abc.dll should be copied to bin/debug folder of main project, but it isn't getting copied there. Why is it not getting copied, any known reasons ?

I found that if ProjectX referenced the abc.dll but didn't directly use any of the types DEFINED in abc.dll, then abc.dll would NOT be copied to the main output folder. (It would be copied to the ProjectX output folder, to make it extra-confusing.)
So, if you're not explicitly using any of the types from abc.dll anywhere in ProjectX, then put a dummy declaration somewhere in one of the files in ProjectX.
AbcDll.AnyClass dummy006; // this will be enough to cause the DLL to be copied
You don't need to do this for every class -- just once will be enough to make the DLL copy and everything work as expected.
Addendum: Note that this may work for debug mode, but NOT for release. See #nvirth's answer for details.

Just a sidenote to Overlord Zurg's answer.
I've added the dummy reference this way, and it worked in Debug mode:
public class DummyClass
{
private static void Dummy()
{
var dummy = typeof(AbcDll.AnyClass);
}
}
But in Release mode, the dependent dll still did not get copied.
This worked however:
public class DummyClass
{
private static void Dummy()
{
Action<Type> noop = _ => {};
var dummy = typeof(AbcDll.AnyClass);
noop(dummy);
}
}
This infomation actually costed me hours to figure out, so I thought I share it.

Yes, you'll need to set Copy Local to true. However, I'm pretty sure you'll also need to reference that assembly from the main project and set Copy Local to true as well - it doesn't just get copied from a dependent assembly.
You can get to the Copy Local property by clicking on the assembly under References and pressing F4.

It looks slick when you make it an assembly attribute
[AttributeUsage(AttributeTargets.Assembly)]
public class ForceAssemblyReference: Attribute
{
public ForceAssemblyReference(Type forcedType)
{
//not sure if these two lines are required since
//the type is passed to constructor as parameter,
//thus effectively being used
Action<Type> noop = _ => { };
noop(forcedType);
}
}
The usage will be:
[assembly: ForceAssemblyReference(typeof(AbcDll.AnyClass))]

Ran into this same issue. Background info: before building, I had added a new Project X to the solution. Project Y depended on Project X and Project A, B, C depended on Project Y.
Build errors were that Project A, B, C, Y, and X dlls could not be found.
Root cause was that newly created Project X targeted .NET 4.5 while the rest of the solution projects targeted .NET 4.5.1. Project X didn't build causing the rest of the Projects to not build either.
Make sure any newly added Projects target the same .NET version as the rest of the solution.

Not sure if this helps but for me, many times I reference a DLL (which automatically adds it to the bin folder of course). However that DLL might need additional DLLs (depending on what functions I'm using). I do NOT want to reference those in my Project because they just simply need to end up in the same folder as the DLL I am actually using.
I accomplish this in Visual Studio by "Adding an existing file". You should be able to add it anywhere except the Add_data folder. personally I just add it to the root.
Then change the properties of that file to ...
Build Action = None (having this set to something like Content actually copies the "root" version to the root, plus a copy in the Bin).
Copy to output folder = Copy if Newer (Basically puts it in the BIN folder only if it is missing, but doesn't do it after that)
When I publish.. my added DLL's only exists in the BIN folder and nowhere else in the Publish location (which is what I want).

You could also check to make sure the DLLs you're looking for aren't included in the GAC. I believe Visual Studio is being smart about not copying those files if it already exists in the GAC on the build machine.
I recently ran in this situation where I'd been testing an SSIS package that needed assemblies to exist in the GAC. I'd since forgotten that and was wondering why those DLLs weren't coming out during a build.
To check what's in the GAC (from a Visual Studio Developer Command Prompt):
gacutil -l
Or output to a file to make it easier to read:
gacutil -l > output.txt
notepad.exe output.txt
To remove an assembly:
gacutil -u MyProjectAssemblyName
I should also note, that once I removed the files from the GAC they were correctly output in the \bin directory after a build (Even for assemblies that were not directly referenced in the root project). This was on Visual Studio 2013 Update 5.

If you right Click the referenced assembly, you will see a property called Copy Local. If Copy Local is set to true, then the assembly should be included in the bin. However, there seams to be a problem with Visual studio, that sometimes it does not include the referenced dll in the bin folder... this is the workaround that worked for me:

In my case, it was the stupidest thing, caused by a default behavior of TFS/VS that I disagree with.
Since adding the dll as a reference to the main project did not work, I decided to add it as an "Existing Item", with Copy Local = Always. Even then the file was not there.
Turns out that, even though the file is present on the VS Solution and everything compiled both locally and on the server, VS/TFS did not add actually add the file to source control. It was not included on the "Pending Changes" at all. I had to manually go to the Source Control Explorer and explicitly click on the "Add items to folder" icon.
Stupid because I've been developing for 15 years in VS. I've run into this before, I just did not remember and somehow I missed it because everything still compiled because of the file being a regular reference, but the file that was added as Existing Item was not being copied because it did not exist on the source control server.
I hope this saves someone some time, since I lost 2 days of my life to this.

Issue:
Encountered with a similar issue for a NuGet package DLL (Newtonsoft.json.dll) where the build output doesn't include the referenced DLL. But the compilation goes thru fine.
Fix:
Go through your projects in a text editor and look for references with "Private" tags in them. Like True or False. “Private” is a synonym for “Copy Local.” Somewhere in the actions, MSBuild is taking to locate dependencies, it’s finding your dependency somewhere else and deciding not to copy it.
So, go through each .csproj/.vbproj file and remove the tags manually. Rebuild, and everything works in both Visual Studio and MSBuild. Once you’ve got that working, you can go back in and update the to where you think they need to be.
Reference:
https://www.paraesthesia.com/archive/2008/02/13/what-to-do-if-copy-local-works-in-vs-but.aspx/

Make sure that the dependent DLL used by you does not have target .NET Framework higher than the target .NET framework of your project's Application.
You can check this by selecting your project, then press ALT+ENTER, then select Application from left side and then select Target Framework of your project.
Suppose,
dependent DLL Target Framework = 4.0 and
Application DLL Target Framework = 3.5 then change this to 4.0
Thank you!

This is a slight tweak on nvirth's example
internal class DummyClass
{
private static void Dummy()
{
Noop(typeof(AbcDll.AnyClass));
}
private static void Noop(Type _) { }
}

I would do add it to Postbuild events to copy necessary libraries to the output directories. Something like XCopy pathtolibraries targetdirectory
You can find them on project properties -> Build Events.

TLDR; Visual Studio 2019 may simply need a restart.
I encountered this situation using projects based on Microsoft.NET.Sdk project.
<Project Sdk="Microsoft.NET.Sdk">
Specifically:
Project1: targets .netstandard2.1
references Microsoft.Extensions.Logging.Console via Nuget
Project2: targets .netstandard2.1
references Project1 via a Project reference
Project2Tests: targets .netcoreapp3.1
references Project2 via a Project reference
At test execution, I received the error messaging indicating that Microsoft.Extensions.Logging.Console could not be found, and it was indeed not in the output directory.
I decided to work around the issue by adding Microsoft.Extensions.Logging.Console to Project2, only to discover that Visual Studio's Nuget Manager did not list Microsoft.Extensions.Logging.Console as installed in Project1, despite it's presence in the Project1.csproj file.
A simple shut down and restart of Visual Studio resolved the problem without the need to add an extra reference. Perhaps this will save someone 45 minutes of lost productivity :-)

You may set both the main project and ProjectX's build output path to the same folder, then you can get all the dlls you need in that folder.

NO NEED FOR DUMMY IN CODE
Just :
add a Reference to the Executeable Project
or/and ensure that the reference in the executeable project has "Copy Local" set to TRUE (which was my "fault") is seems that this "overwrote" the setting in the base referenced library-project...

Other than the common ones above, I had a multi-project solution to publish. Apparently some files target different frameworks.
So my solution: Properties > Specific Version (False)

Add the DLL as an existing item to one of the projects and it should be sorted

VS2019 V16.6.3
For me the problem was somehow the main .proj file ended up with an entry like this for the project whose DLL wasn't getting copied to the parent project bin folder:
<ProjectReference Include="Project B.csproj">
<Project>{blah blah}</Project>
<Name>Project B</Name>
<Private>True</Private>
</ProjectReference>
I manually deleted the line <Private>True</Private> and the DLL was then copied to the main project bin folder on every build of the main project.
If you go to the reference of the problem project in the references folder of the main project, click it and view properties there is a "Copy Local" setting. The private tag equates to this setting, but for me for some reason changing copy local had no effect on the private tag in the .proj file.
Annoyingly I didn't change the copy local value for the reference, no idea how it got set that way and another day wasted tracking down a stupid problem with VS.
Thanks to all the other answers that helped zone me in on the cause.
HTH

I had a similar issue in which a DLL I had included in the project as content and 'Copy always' set, wasn't being copied to the bin folder. I solved this by adding a dependentAssembly reference to the DLL in the app.config.

Visual Studio C# .dll vs. project referencing

I have two C# projects in my Visual Studio solution. Project B needs to reference code in Project A. Both projects need to be compiled to dll's and then used in an application.
In Project B I can set a reference to project A and that allows things to compile. But when I actually use the resulting dll's in my application it throws a missing assembly reference error.
My current solution is to tell Project B to reference the bin/debug/ProjectA.dll. Everything works when running the application with this configuration. But this solution has a number of problems. For instance, any code written in Project A that B relies on wont be visible to B until A has been rebuilt. And building the solution relies on A being built first.
Is there a way that I can add a reference to Project A but have the resulting dll built so it looks for the ProjectA.dll reference and not the project itself? I expect there is, but my google searching has resulted in no answers.

For instance, any code written in Project A that B relies on wont be visible to B until A has been rebuilt. And building the solution relies on A being built first.
This is not a problem, this is, in my view, a benefit. As you are guaranteed to not be able access functionality which is not there. In case of a new functionality, one may say, it's not a big deal: I can not find it, got an exception/error so I know something went wrong. But what about updated code ? In this way you are guaranteed that B will use only most updated version of A.
Is there a way that I can add a reference to ProjectA but have the resulting dll built so it looks for the ProjectA.dll reference and not the project itself?
You may simply implement post-build event on your project A which copies it and all dependent DLLs in some predefined central location, where B.dll will be copied too. If your B.dll depends on A.dll, OS, following default behavior, will search for A.dll in the same folder where B.dll is, for first, before checking %PATH% variable content.

DLL reference not copying into project bin

Project A references Project B, and Project B references an external DDL (restored using NuGet). The DLL should get copied into Project A's bin folder (along with Project B's DLL):
In my case, when running Project A, I get the following exception thrown:
Could not load file or assembly 'PostSharp, Version=3.2.18.0,
Culture=neutral, PublicKeyToken=b13fd38b8f9c99d7' or one of its
dependencies. The system cannot find the file specified.
The DLL is not being copied into Project A's bin. All other external references from Project B are being copied across just fine, which is what is confusing for me.
Copy Local is set to true for all references involved. Example:
How do I do this?
Note: Using Visual Studio 2013.

The options that I found were to:
Add a reference to PostSharp in Project A.
Add dummy code in Project B so that the compiler would detect that the reference is being used.
Add a build event to force copy the DLL.
I don't like any of the above solutions. They are hacks in my opinion and will only make for a more unmaintainable solution in the long run.
I have fixed the problem by using a common output directory. This seems to be a recommended solution by many. I have also experienced much faster build times. See this Stackoverflow post.

When I ran into this problem it was because I changed a project's name, but did not change the assembly name - it was identical to the assembly name of another project in the solution.

I've added some dummy (unused) code on Project B, making reference to the DLL needed.
Thus, the compiler will guess that it must copy the DLL into project A output.

Copying indirectly referenced assembly to output directory - assembly is missing [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How does Copy-local work?
I have following situation:
there's a project named OLAF.Tools, and that project references Microsoft.Data.SqlXml in C:\Program Files\SQLXML 4.0\bin\Microsoft.Data.SqlXml.dll. Reference Copy Local property is set to True. When I build that project in bin directory I can see both OLAF.Tools.dll and Microsoft.Data.SqlXml.dll
there's a console application named OLAF.Generator, and that application references OLAF.Tools (I've added reference using Project tab). When I build that application in bin directory I can see only OLAF.Generator.exe and OLAF.Tools.dll - there's no Microsoft.Data.SqlXml.dll, what supprises me. Another wierd thing is that even though that dll is missing application is executing properly.
So my questions are:
why Microsoft.Data.SqlXml.dll is not copied to bin folder of OLAF.Generator console application?
how application resolves directory where Microsoft.Data.SqlXml.dll can be found?
Thanks,Pawel
EDIT 1: (after response from Marc Gravell)
#Marc Gravell: Your answer gave me food for thought, as I could swore that I could always see indirectly dependant assemblies in main application's bin directory. And IMHO I don't agree with you - with all due respect :)
Of course, references are not cascaded physically (we're are talking about strong relationship to classes, interfaces etc) - and it's exactly what I wanted to achieve when building OLAF.Tools library. That library provides a level of abstraction, it contains factories, and one factory accepts as a parameter string and returns interface. One particular implementation of that interface uses Microsoft.Data.SqlXml components. As a result,
OLAF.Generator uses interface that is located in OLAF.Tools, but doesn't know about components in Microsoft.Data.SqlXml.
Apart from that (I think we both know what I tried to explain in preceding paragraph), when building application, dependant assemblies should be copied (if Copy Local is set to TRUE). I just wrote sample application, Project B lib has reference to Project A lib, and Project C (console app) has reference to Project B. In Project C's bin directory I can see all: Project A.dll, Project B.dll & Project C.exe. So in discussed scenario, the reason why Microsoft.Data.SqlXml doesn't end up in OLAF.Generator bin folder has something to do with that assembly itself.
Does compiler/visual studio knows that Microsoft.Data.SqlXml is located in directory which is automatically probed (or it's in GAC) and this is the reason why that assembly is not copied?
EDIT 2: I've just checked GAC, and indeed, Microsoft.Data.SqlXml.dll is installed in GAC.

How does Copy-local work? log4net.dll is not being copied to MyProject output directory - this is answer to my question. When library is installed in GAC, it won't be copied even though COPY LOCAL setting is used.

References are not automatically cascaded, so adding a reference to OLAF.Tools does not also add a reference to SQLXML. If you want to deploy SQLXML with your exe, then the most convenient way to do that is to explicitly add a reference to SQLXML from your exe, and set it to copy local. Without this, it is not deployed. Basically, the onus is on the developer to decide which files are actually needed at runtime (which is often a subset of the references used, and depends on a number of deployment decisions which only you can know).
Re how it is resolved at runtime... the probing paths are a bit of a black art, mainly meaning "the app folder", but it depends on the config, and indeed the GAC may be consulted. You also get an opportunity to provide your own resolver, via AppDomain.Current.AssemblyResolve.

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