Duplicate AssemblyVersion Attribute

Question

I have a project that generates following error on compilation      error CS0579  Duplicate  AssemblyVersion  attribute   I have checked the file AssemblyInfo cs and it looks like there is no duplication there   I found this article on MSDN which addresses a similar problem and following the suggestion in this article fixes the problem as well    Can anyone tell me what s going on here  Does it happen only in case of having two or more projects with classes having similar names  Or is it something else

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I got the error Just after switching from  NET Framework to  NET Core   I have 2 class library projects in my Visual Studio solution   I realized that 1 of the projects has a file named AssemblyInfo cs while the other project does not have the file   The file is located under the Properties folder  I simply delete the Properties folder and all works fine

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This usually happens for me if I compiled the project in Visual Studio 2017  amp  then I try to rebuild  amp  run it with  NET Core with the command line command  dotnet run    Simply deleting all the  bin   amp   obj  folders - both inside  ClientApp   amp  directly in the project folder - allowed the  NET Core command  dotnet run  to rebuild  amp  run successfully

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I ran into this recently with no changes to source  but after experimenting with some new project references  I got into a state where this error was appearing even after reverting all changes in the branch  Cleaning the branch resolved it for me  git clean -xfd

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When converting an older project to  NET Core  most of the information that was in the  AssemblyInfo cs  can now be set on the project itself  Open the project properties and select the Package tab to see the new settings     The Eric L  Anderson s post   Duplicate    System Reflection AssemblyCompanyAttribute    attribute   describes 3 options      remove the conflicting items from the AssemblyInfo cs file  completely delete the file or disable GenerateAssemblyInfo  as suggested in another answer by Serge Semenov

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I had the same error and it was underlining the Assembly Vesrion and Assembly File Version so reading Luqi answer I just added them as comments and the error was solved     AssemblyVersion is the CLR version  Change this only when making breaking    changes    assembly  AssemblyVersion  3 1         AssemblyFileVersion should ideally be changed with each build  and should help identify the origin of a build    assembly  AssemblyFileVersion  3 1 0 0

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I got this error when I did put 2 projects in the same directory  If I have a directory with an solution and I put a separate Web and Data directory in it compiles right

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I have also run into this issue in the past  so I am going to assume that your build process provides assembly information separately to providing versioning  And that causes a duplication as your project also has that info in the AssemblyInfo cs file  So remove the file and I think it should work

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obj Debug netstandard2 0 PacktLibrary AssemblyInfo cs 15 12   error CS0579  Duplicate  System Reflection AssemblyConfigurationAttribute  attribute  c  Users John Tosh1 Documents C 8 0and NetCore3 0 Code Chapter05 PacktLibrary PacktLibrary csproj  obj Debug netstandard2 0 PacktLibrary AssemblyInfo cs 16 12   error CS0579  Duplicate  System Reflection AssemblyFileVersionAttribute  attribute  c  Users John Tosh1 Documents C 8 0and NetCore3 0 Code Chapter05 PacktLibrary PacktLibrary csproj  obj Debug netstandard2 0 PacktLibrary AssemblyInfo cs 17 12   error CS0579  Duplicate  System Reflection AssemblyInformationalVersionAttribute  attribute  c  Users John Tosh1 Documents C 8 0and NetCore3 0 Code Chapter05 PacktLibrary PacktLibrary csproj  obj Debug netstandard2 0 PacktLibrary AssemblyInfo cs 18 12   error CS0579  Duplicate  System Reflection AssemblyProductAttribute  attribute  c  Users John Tosh1 Documents C 8 0and NetCore3 0 Code Chapter05 PacktLibrary PacktLibrary csproj  obj Debug netstandard2 0 PacktLibrary AssemblyInfo cs 19 12   error CS0579  Duplicate  System Reflection AssemblyTitleAttribute  attribute  c  Users John Tosh1 Documents C 8 0and NetCore3 0 Code Chapter05 PacktLibrary PacktLibrary csproj  obj Debug netstandard2 0 PacktLibrary AssemblyInfo cs 20 12   error CS0579  Duplicate  System Reflection AssemblyVersionAttribute  attribute  c  Users John Tosh1 Documents C 8 0and NetCore3 0 Code Chapter05 PacktLibrary PacktLibrary csproj    I believe my Library folder was corrupted by an inadvertent creation of another class library I deleted the library an all associated file but the problem persisted   I found a workaround by deleting ALL bin and obj folders in the directory  The build was ok previously but found a subfolder that had the same assemblyinfo cs file

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I found this answer on msdn  that explains marking the file as Content and then Copy to Output   If Newer  See article below    https   social msdn microsoft com Forums en-US 8671bdff-9b16-4b49-ba9e-227cc4df31b2 compile-error-cs0579-duplicate-assemblyversion-attribute forum vsgatk  GH

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My error occurred because  somehow  there was an obj folder created inside my controllers folder  Just do a search in your application for a line inside your Assemblyinfo cs  There may be a duplicate somewhere

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In my case  some temporary   cs files generated during compilation got accidentally added to the project   The files were from the obj Debug directory  so they definitely shouldn t have been added to the solution  A   cs wildcard went a little crazy and added them incorrectly   Deleting these files fixed the problem

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I had this issue when my main project was in the same folder as the solution  then I had a separate project in the same solution located in a sub folder  and that separate project used the main project as a reference  This caused the main project to detect the sub folder bin  amp  obj folders which created duplicate references

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I have being struggling with this issue  but my problem was much easier to solve  I had copied OBJ folder to  quot OBJ    quot  name to do some compilation tests  So  I don t know why  this folder was being also compiled  creating the assembly attributes duplication  I simply deleted the  quot OBJ    quot  folder and could compile successfuly

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In my case  there where a subfolder in a project that was a project folder it self    file system    c  projects webapi wepapi csproj c  projects webapi tests wepapitests csproj  solution   webapi  folder and project    tests  folder   tests  folder and project     Then i had to remove the subfolder  tests  from the  webapi  project

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For me it was that AssembyInfo cs and SolutionInfo cs had different values  So check these files as well  I just removed the version from one of them

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This issue is a reference conflict which is mostly peculiar to VS 2017   I solved this same error by simply commenting out lines 7 -14 as well as Assembly version codes at the bottom of the page on AssemblyInfo cs  It removed all the duplicate references and the project was able to build again

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Yet another solution when upgrading core to VS2017 is to remove them in the properties assemblyinfo cs file   Since they now are stored in the project

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If you re having this problem in a Build Pipeline on Azure DevOps  try putting the Build Action as  Content  and Copy to Output Directory equal to  Copy if newer  in the AssembyInfo cs file properties

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There must be already a AssemblyInfo cs file in the project here    To solve  - Delete any one AssemblyInfo cs

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Edit you AssemblyInfo cs and  if  NETCOREAPP3 0       endif  using System Reflection  using System Runtime CompilerServices  using System Runtime InteropServices     General Information about an assembly is controlled through the following    set of attributes  Change these attribute values to modify the information    associated with an assembly    if  NETCOREAPP3 0     assembly  AssemblyTitle   Net Core Testing     assembly  AssemblyDescription   Net Core     assembly  AssemblyConfiguration       assembly  AssemblyCompany       assembly  AssemblyProduct   Net Core     assembly  AssemblyCopyright  Copyright        assembly  AssemblyTrademark       assembly  AssemblyCulture          Setting ComVisible to false makes the types in this assembly not visible    to COM components   If you need to access a type in this assembly from    COM  set the ComVisible attribute to true on that type   assembly  ComVisible false       The following GUID is for the ID of the typelib if this project is exposed to COM  assembly  Guid  000b119c-2445-4977-8604-d7a736003d34        Version information for an assembly consists of the following four values             Major Version         Minor Version         Build Number         Revision       You can specify all the values or you can default the Build and Revision Numbers    by using the     as shown below      assembly  AssemblyVersion  1 0       assembly  AssemblyVersion  1 0 0 0     assembly  AssemblyFileVersion  1 0 0 0      endif

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My error was that I was also referencing another file in my project  which was also containing a value for the attribute  AssemblyVersion   I removed that attribute from one of the file and it is now working properly   The key is to make sure that this value is not declared more than once in any file in your project

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I came across the same when tried add GitVersion tool to update my version in AssemblyInfo cs  Use VS2017 and  NET Core project  So I just mixed both worlds  My AssemblyInfo cs contains only version info that was generated by GitVersion tool  my csproj contains remaingin things  Please note I don t use  lt GenerateAssemblyInfo gt false lt  GenerateAssemblyInfo gt  I use attributes related to version only  see below   More details here AssemblyInfo properties   AssemblyInfo cs   assembly  AssemblyVersion  0 2 1 0     assembly  AssemblyFileVersion  0 2 1 0     assembly  AssemblyInformationalVersion  0 2 1 13 Branch master Sha 119c35af0f529e92e0f75a5e6d8373912d457818      my csproj contains all related to other assemblyu attributes    lt PropertyGroup gt       lt Company gt SOME Company  lt  Company gt   lt Authors gt Some Authors lt  Authors gt   lt Product gt SOME Product lt  Product gt       lt GenerateAssemblyVersionAttribute gt false lt  GenerateAssemblyVersionAttribute gt   lt GenerateAssemblyFileVersionAttribute gt false lt  GenerateAssemblyFileVersionAttribute gt  lt GenerateAssemblyInformationalVersionAttribute gt false lt  GenerateAssemblyInformationalVersionAttribute gt

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Starting from Visual Studio 2017 another solution to keep using the AssemblyInfo cs file is to turn off automatic assembly info generation like this    lt Project Sdk  Microsoft NET Sdk  gt     lt PropertyGroup gt       lt GenerateAssemblyInfo gt false lt  GenerateAssemblyInfo gt     lt  PropertyGroup gt   lt  Project gt    I personally find it very useful for projects which need to support both  NET Framework and  NET Standard

[c#] Duplicate AssemblyVersion Attribute

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