Why am I getting Assembly dll must be strong signed in order to be marked as a prerequisite

Question

I m trying to compile my excel addin using C  4 0  and started to get this problem when building my project in Visual Studio  It s important to tell you that I haven t had this problem before  What could cause this to happen

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I got the similar compiler error  Once I add the dependent project of the dll file to the solution  issue resolved

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After trying most of the solutions here  I finally just added a reference to the project from the click once project  this changed it to Include  Auto  from Include and it finally worked

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Unloading and reloading the problem project solved it for me

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I went to publish  application files  found the dll throwing the error changed it to  Include  from  Include  Auto     I can now publish

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If you have changed your assembly version or copied a different version of the managed library stated in the error you may also have previously compiled files referencing the wrong version  A  Rebuild All   or deleting you  bin and  obj  folders as mentioned in an earlier comment  should fix this case

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Deleting the DLL  where the error is occurred  and re-building the solution fixed my problem  Thanks

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I had this in a solution w  6 projects   One of my projects was referring to the named assembly as a file reference  The others were all pointing to the project reference    I usually get a different error in these cases    My solution was to delete the named assembly anywhere it was referenced and add it back   Once I worked through the project  ths problem disappeared   Before doing this  I tried cleaning the solution as well as making sure none of the projects were signed    hope it helps someone

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I ve had this problem  It happened because i had many projects pointing to the same assembly but from different versions  I solve it selecting the same version to all projects in my solution

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When this happened to me with the WindowsAPICodePack after I updated it  I just rebuilt the solution   Build-- Rebuild Solution

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If its a mismatch of a dependencies dependencies  go to the NuGet package manager at the solution level and check the Update and Consolidate tabs  harmonise it all

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I also bump into kind of problem  all I just had to do is delete the  dll  can be found in reference  that causing the error and add it again    Works like a charm

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Is your assembly properly signed   To check this  press Alt Enter on your project  or right click  then Properties   Go to  Signing   Verify that the check box  Sign the assembly  is checked and the strong name key file is selected and  Delay sign only  is unchecked

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My guess is that you re not working with strongly named assemblies  I ve had this error when two projects reference slightly different versions of the same assembly and a more dependent project references these projects  The resolution in my case was to remove the key and version information from the assembly name in the  csproj files  it didn t matter anyway   and then do a clean build   Changes between the different assembly versions were compatible with the parts of the solution referring to them  If this is not the case with you  you might have to do some more work to resolve the issue   NuGet  With NuGet it s easy to get into this situation if    You install a package to one project in your solution  A new version of that package is deployed to the package source  You install it to another project in the same solution    This results in two projects in your solution referencing different versions of that package s assemblies  If one of them references the other and is a ClickOnce app  you ll see this problem   To fix this  issue the update-package  package name  command at the Nuget Package Manager Console to bring everything up to a level playing field  at which point the problem goes away   You should manage NuGet packages at the solution level rather than at the project level unless there is a compelling reason not to  Solution level package management avoids the potential of multiple versions of dependencies  When using the management UI  if the Consolidated tab shows 1 or more packages have multiple versions  consider consolidating them to one

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you need to sign the assembly with a key  Go in the project properties under the tab signing

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What helped me was I went onto Package Manager Solution and looked at the installed package which was causing the issue   I saw that several projects were referencing the same package but different versions  I aligned them based on my needs and it worked

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Try with update-package -reinstall -ignoredependencies

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If you tried all the other answers in this question and you   Have multiple projects in your solution Have a project  Project A  that references another project  Project B   whose project references a NuGet package  In Project A  you used Intellisense ReSharper to bring in the reference to the NuGet package referenced in Project B  this can happen when a method in Project B returns a type provided by the NuGet package and that method is used in Project A  updated the NuGet package via NuGet Package Manager  or CLI       you may have separate versions of the NuGet packages DLL in your projects  References  as the reference created by Intellisense ReSharper will be a  quot normal quot  reference  and not a NuGet reference as expected  so the NuGet update process won t find or update it  To fix this  remove the reference in Project A  then use NuGet to install it  and make sure the NuGet packages in all projects are the same version   as explain in this answer   Life Pro Tip  This issue can come up whenever ReSharper Intellisense suggests to add a reference to your project  It can be much more deeply convoluted than the example above  with multiple interweaving projects and dependencies making it hard to track down  If the reference being suggested by ReSharper Intellisense is actually from a NuGet package  use NuGet to install it

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Now Here is a different approach to the problem    Right click on the project and select the  Unload Project  option  You will notice you project becomes unavailable   Right click on the unavailable project and select the  Edit  option  Scroll down to the    lt  ItemGroup     tag that contains all the resource tags  Now go to the reference that has been displayed on the error list  you will notice it it uses a single tag  i e   lt  Reference Include  assemble name here  Version 0 0 0 0  Culture neutral     gt    Change that to look as follows        lt Reference Include  assemble name here  Version 1 0 0 0  Culture neutral  processorArchitecture MSIL   gt       lt  Private  gt  True  lt    Private  gt       lt  HintPath  gt  path here assemble name here dll  lt    HintPath  gt   lt    Reference  gt     Save your changes  Right click on the unavailable project again and click on the  Reload Project  option  then build

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I recently hit this problem   In my case  I have NuGet packages on different assemblies   What I had was different versions of the same NuGet packages associated with my own assemblies  My solution was to use the NuGet package manager upon the Solution  as opposed to the individual projects   This enables a  consolidation  option  where you can upgrade your NuGet packages across as many projects as you want - so they all reference the same version of the assembly  When I did the consolidations  the build failure disappeared

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When I had this problem I fixed it by turning off the  Enable ClickOnce security settings    Menu  Project    Project name  Properties      Security tab    Enable ClickOnce security settings  check box

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There were too many projects in my solution to go through and individually update so I fixed this by    Right-clicking my solution and selecting  Manage NuGet Packages for Solution     Going to the Updates tab Finding the affected package and selecting Update Clicked OK and this brought all instances of the package up to date

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I encountered this problem after migrating an Excel Addin from packages config to PackageReference  Seems to be related to this issue   The following works as a crude workaround if you re not using ClickOnce  it will omit all the dependency information from the  manifest file     Unload project  edit  csproj Find the section looking like this    lt  -- Include additional build rules for an Office application add-in  -- gt   lt Import Project    VSToolsPath  OfficeTools Microsoft VisualStudio Tools Office targets  Condition     VSToolsPath            gt   Edit a renamed copy of the referenced  targets file  in my case  the file resolved to C  Program Files  x86  Microsoft Visual Studio 2017 Professional MSBuild Microsoft VisualStudio v15 0 OfficeTools Microsoft VisualStudio Tools Office targets and I made a copy Microsoft VisualStudio Tools Office FIX targets in the same folder - didn t check if it works from a different folder   Find the GenerateApplicationManifest element and change its attribute Dependencies    DependenciesForGam   to Dependencies     Change the section found in 2  to reference your edited  targets file instead    This will have to be repeated whenever the version of the  targets file shipped with VS is updated  or you won t get the updates   but I m hoping it will be fixed soon

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Just go to Publish -  Application File -  And change the effected dll publish status from prerequisite to include  This worked for me

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If your main project using some library projects and have reference to them  you can cause this problem if your project reference to a assembly dll file instead to library project when you change something in your library project  ex  rename a class    You can check all references to your main project by view in Object Browser window  menu View- Object Browser   A reference to a dll file always has a version number  Ex  TestLib  1 0 0 0   Solution  delete the current reference of your main project to the library project and add reference to that library project again

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Adding my solution for this issue for anyone it might help   I had a ClickOnce solution throwing this error  The app referenced a common  Libs  folder and contained a project reference to a Foo dll  While none of the projects in the solution referenced the static copy of the Foo dll in the  Libs  folder  some of the references in that folder did  ie  my solution had refs to Libs Bar dll which referenced Foo dll   Since the CO app pulled all the dependencies from Libs as well as their dependencies  both copies were going into the project  This was generating the error above   I fixed the problem by moving my Libs Foo dll static version into a subfolder  Libs Fix Foo dll  This change made the ClickOnce app use only the project version of the DLL and the error disappeared

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This is caused when you change the version of the  dll that is referenced  You need to delete all items  or the  dll in the target build folder

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See this answer      Go to the publish page and click on  Application Files   From there you should see a list of your DLL s  Ensure that the ones that are giving you trouble have their Publish Status marked as  Include  rather than  Prerequisite

[c#] Why am I getting 'Assembly '*.dll' must be strong signed in order to be marked as a prerequisite.'?

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