Dependent DLL is not getting copied to the build output folder in Visual Studio

Question

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 ?

how do you use your 'ProjectX' in the main project - what's the type of the project, target etc. — NSGaga-mostly-inactive, Apr 04 '13 at 17:45
I had the same issue and this answer solved my problem: http://stackoverflow.com/a/8213977/174469 — Gordon Tucker, Sep 19 '13 at 17:44
Possible duplicate of [Msbuild doesn't copy references (dlls) if using project dependencies in solution](http://stackoverflow.com/questions/1132243/msbuild-doesnt-copy-references-dlls-if-using-project-dependencies-in-solution) — sirdank, Jun 02 '16 at 13:17
there is `RestoreProjectStyle` [solution available](https://stackoverflow.com/a/50510696/940182). The idea is to set `PackageReference` for each .Net Framework project in the solution. — oleksa, May 20 '20 at 09:43

Overlord Zurg · Answer 1 · 2016-12-16T14:23:04.973

116

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.

edited Dec 16 '16 at 14:23

answered Jul 18 '14 at 15:20

Overlord Zurg

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This seems like a hack. Adding the reference to the main project seems to be enough. – Mike K Mar 09 '15 at 17:53
3

It IS a hack, but as today's CodeProject news taught us, even compilers can be wrong! – Overlord Zurg Mar 10 '15 at 19:21
Adding a reference in the main project did not work for me. Only adding the dummy reference got the compiler to copy the referenced dll. – Alex Fairchild May 12 '15 at 20:18
1

Adding a reference to the main project wasn't enough. I had to create a dummy field in one of the classes to get the assembly copied over to the output directory. This approach is acceptable for test code, as is the case here, but I'd rather see a more robust solution for solving this issue for production code. – Alfred Myers Sep 30 '15 at 18:53
4

How crazy things can be. @OverlordZurg your solution worked as I had a reference to the dependent dll in my XAML (WPF) and it didn't copy the DLL to the main project until I add a simple dummy reference as you told ... Thanks anyway – Mohsen Afshin Oct 14 '15 at 09:11
1

This is the way I always use. I don't want to put a reference to every dependent project. It seems wrong to me.. – sotn Oct 21 '15 at 13:52
5

@MohsenAfshin I had the same issue---I was referencing a dependent DLL in XAML. Instead of declaring a dummy variable, however, I simply named the component I was using in XAML, and that was enough to cause its assembly to be copied. – redcurry Nov 18 '15 at 20:51
6

@MikeK Adding it to the main project (which doesn't actually directly depend on it) is an even bigger hack, imo. Then you have to manage it two places ("manage" as in upgrade or remove). With *this* hack, at least you get a nice compile time error reminding you to remove this hack when you remove the dependency, and you still only need to update it in one place. – jpmc26 Sep 21 '16 at 19:35
1

Was happening to me for a data layer library which only used extension methods. (Dapper) When the consumer of the library was built, it didn't detect the dependency correctly and didn't copy the dapper assembly, resulting in an ugly FileNotFound exception. – Nathan Dec 15 '16 at 13:14
1

Calling `GC.KeepAlive(typeof(SomeTypeInProblematicAssembly));` at some point is sufficient for the dependency to be traced. – Fls'Zen Oct 06 '17 at 20:07
WpfAnimatedGif only adds attached properties to XAML elements, so wasn't being copied and there are no constructable objects in the library. This line in the window constructor works for me, though, both in Debug and Release: `string copyMePlease = WpfAnimatedGif.ImageBehavior.AutoStartProperty.Name;` – Matt Gregory Apr 07 '19 at 14:04

score 82 · Answer 2 · answered Sep 28 '16 at 19:12

82

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.

answered Sep 28 '16 at 19:12

nvirth

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in release mode, optimizer assume that "dummy" is not used so this line is unnecessary and should be removed. but when you use "dummy" in code, optimizer doesn't assume itis unnecessary. – Yucel Oct 21 '16 at 14:42
1

this doesn't work for me.AbcDll.AnyClass still isn't copied to other project – Matthew Lock Mar 15 '17 at 23:55
3

Make sure `AbcDll.AnyClass` is used as a public field or property on a public class, then it will work. If you use it in a method body like this the compiler doesn't _see it_. It will delay load this assembly, not what you want to happen. – John Leidegren May 04 '18 at 11:30

score 59 · Answer 3 · answered Apr 04 '13 at 16:35

59

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.

answered Apr 04 '13 at 16:35

Mike Perrenoud

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@Brij, is the assembly referenced from the **main project** you want it in? As I stated, **I'm pretty sure** you need to reference from that project as well - dependent assemblies aren't copied over like that. If that were the case you wouldn't need to add the assemblies to all relevant projects when using NuGet. – Mike Perrenoud Apr 04 '13 at 16:42
I created a sample solution in Visual Studio. In that, the dependent dll is getting copied in the main project. – Brij Apr 04 '13 at 17:09
@Brij, what's the difference between the two solutions then? Are you referencing the outside assembly exactly the same way as in the other solution? – Mike Perrenoud Apr 04 '13 at 17:11
yes, the dll is at desktop and the project is referring that dll. And the project is referenced in main project. – Brij Apr 04 '13 at 17:14
@Brij, then that must mean the referenced project, from the main project, is setup differently in the working solution. Press `F4` on the references project under the main project's References and see what the differences are between the two. – Mike Perrenoud Apr 04 '13 at 17:21
No difference other than the name and path. – Brij Apr 04 '13 at 17:23
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/27573/discussion-between-michael-perrenoud-and-brij) – Mike Perrenoud Apr 04 '13 at 17:25
1

what was the conclusion here? It seems to me that you are right - dependent references are not copied even if CopyLocal is set to true - what is the logic behind that? – mcmillab Jul 23 '13 at 05:10
29

@mcmillab, in short Visual Studio doesn't **infer** dependencies from other dependent projects. If project A references project B, project A will need to have all of project B's references. It works nicely when all project B needs is .NET assemblies, but if it's a 3rd party assembly you must add the reference to both projects. – Mike Perrenoud Jul 23 '13 at 10:38
13

@MichaelPerrenoud I don't think that's true. If you look at a detailed MSBuild output you will see calls to [ResolveAssemblyReference](http://msdn.microsoft.com/en-us/library/9ad3f294.aspx) which states it "includes second and nth-order dependencies". This also concurs with what I see in my bin folders (n-th dependencies get copied). The issue is there are some caveats about what is copied, mostly around GAC and indirect references (Add Reference is sometimes not enough) – Jack Ukleja Sep 25 '14 at 16:16
I've seen this myself- My model project references a 3rd party dll (A), which requires another 3rd party dll (B)- I reference model from my web project and publish, and B.dll doesn't appear causing a silent problem breaking part of the system. Very annoying. – Shawson Apr 23 '15 at 13:46
I have seen the same thing. What is the conclusion? – Frank Liu May 08 '15 at 01:43
2

My current experience is that this will work *except* for 'copied' dependencies: project A.net references external C++ dlls as files which are 'copy always'. Project B.net references Project A. On build, B/Debug includes the C++ dlls. However, when I build Application X, which references Project B, the C++ dlls *sometimes* get copied (seems to be only if I do a Rebuild). – Benjol Feb 11 '16 at 10:11
2

I'm pretty sure this is *wrong*. It doesn't need to *infer dependencies*, it just needs to *copy output* (from one project's bin to another's), which MSBuild does, at least normally. – jpmc26 Sep 21 '16 at 19:39
1

@MikePerrenoud I dont think thats true either (that you need to reference all references that Project B has). I have this issue now, where ProjectB is references from my MainProject and I get the error. I was hoping that VS understood that reference chain went like _"ProjectA-->ProjectB-->ProjectC-->multiple DLLs including the 'cannot resolve'-DLL"_. But it fails. But, in another project, I have "ProjectOther-->ProjectB-->ProjectC-->..." but ProjectOther ALSO references ProjectC directly, and then manages to run as expected. – Ted Apr 03 '18 at 03:04
@Ted I think this behavior is actually proven via NuGet. When you reference a NuGet package in ProjectA, then reference ProjectA assembly in ProjectB, you'll have to add that NuGet package to ProjectB for the build to work. – Mike Perrenoud Apr 03 '18 at 08:37
1

Nops, I dont think so. Im not sure what u mean with "proven via NuGet" or "NuGet package", but I have many many DLL-references in _Project C_ that are not referenced in _Project B_ or _Project A_ in my chain, that looks like this: _Project A ==> Project B ==> Project C_. And it builds, but sometimes fails in runtime as described above. – Ted Apr 04 '18 at 09:41
To put it simply: your project must reference dependencies of its dependencies. Which I find completely nonsensible. – sigod May 20 '20 at 10:09

Aryéh Radlé · Answer 4 · 2017-09-25T12:58:07.843

38

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))]

edited Sep 25 '17 at 12:58

answered Sep 25 '17 at 12:42

Aryéh Radlé

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Thank you, but for me this only does something when I add the assembly attribute to the dependency (Project X), which already references the AbcDll.AnyClass. And then, it doesn't do more than normally, where it copies the AbcDll to the dependency's output directory. It still does not copy it to the main dependent project's output. And I cannot add the attribute to the dependent assembly unless I also add a reference to AbcDll. When I do that, AbcDll already gets copied without the attribute. – J S May 16 '20 at 09:19

score 28 · Answer 5 · answered Feb 22 '15 at 18:27

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.

Referenced projects may be an older version of .NET. I'm able to reference a project built for .NET 4 by a project built for .NET 4.5. — redcurry, Nov 18 '15 at 20:53

score 19 · Answer 6 · answered Dec 06 '16 at 22:30

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).

score 10 · Answer 7 · answered Oct 03 '16 at 18:09

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.

Thanks, you are right, MSBuild will not copy dll to output folder if it found them in the GAC. — John-Philip, May 11 '17 at 06:59

score 3 · Answer 8 · answered Jun 27 '18 at 16:22

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.

I can't thank you enough... you saved me so much time. This was solution for me. It also exposed the root problem, the DLL I added as a reference matched a `gitignore` pattern, so when adding as a reference it did not add to the project. You MUST manually add the file to source control!!! — Mattkwish, Mar 06 '19 at 16:12

score 2 · Answer 9 · answered Jul 30 '17 at 01:42

2

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 _) { }
}

answered Jul 30 '17 at 01:42

maca134

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Hooman Bahreini · Answer 10 · 2018-06-06T10:29:29.313

2

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:

edited Jun 06 '18 at 10:29

answered Jan 26 '18 at 03:06

Hooman Bahreini

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Copy Loal was disabled, this helped https://stackoverflow.com/questions/15526491/why-is-the-copy-local-property-for-my-reference-disabled – codemirror Apr 01 '19 at 07:42

score 2 · Answer 11 · answered Apr 06 '18 at 22:06

2

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.

answered Apr 06 '18 at 22:06

chethan jain

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This worked for me, and I think this is the better answer. The dummy reference solution works, but it's a hack, whereas a post-build rule is a clean way to accomplish the same result. – Kevin Fichter May 02 '19 at 19:47

score 2 · Answer 12 · edited Oct 26 '20 at 07:40

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/

score 2 · Answer 13 · answered May 01 '20 at 14:49

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 :-)

Actually I restarted the whole PC on my way of testing things but it worked for me — Noman_1, Jun 18 '20 at 09:49
I'm having the same problem with SDK project .NET5 , I tried this solution but unfortunately it didn't work for me, even after restart the PC :( — SomeCode.NET, Dec 19 '20 at 21:09

score 1 · Answer 14 · edited May 07 '21 at 10:58

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!

Cadburry · Answer 15 · 2017-06-07T09:34:15.013

1

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...

edited Jun 07 '17 at 09:34

answered Jun 07 '17 at 08:34

Cadburry

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YantingChen · Answer 16 · 2016-06-23T06:21:32.703

0

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.

edited Jun 23 '16 at 06:21

answered Apr 20 '16 at 06:29

YantingChen

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score 0 · Answer 17 · answered May 04 '17 at 13:20

0

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)

answered May 04 '17 at 13:20

RicL

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score 0 · Answer 18 · answered Oct 13 '17 at 07:50

0

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

answered Oct 13 '17 at 07:50

abhijithkarkal

21
5

score 0 · Answer 19 · answered Jul 10 '20 at 14:48

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

Dependent DLL is not getting copied to the build output folder in Visual Studio

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