Found conflicts between different versions of the same dependent assembly that could not be resolved

Question

When I clean and then build my solution that has several projects  the output window reports that the build succeeded  However  when I view the Error List Window  it shows me this warning      Found conflicts between different versions of the same dependent assembly that could not be resolved   These reference conflicts are listed in the build log when log verbosity is set to detailed     C  Program Files  x86  MSBuild 12 0 bin Microsoft Common CurrentVersion targets   When I double-click this message  it opens the C  Program Files  x86  MSBuild 12 0 bin Microsoft Common CurrentVersion targets file but I don t understand anything in it   I am using Visual Studio Express 2013 for the Web   How do I find out what s wrong and with which DLL and how do I then make the warning go away

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I found that  sometimes  nuget packages will install  what I m guessing are   NET Core required components or other items that conflict with the already-installed framework  My solution there was to open the project   csproj  file and remove those references  For example  System IO  System Threading and such  tend to be added when Microsoft Bcl is included via some recently installed NuGet package   There s no reason for  specific versions of those in my projects  so I remove the references and the project builds  Hope that helps   You can search your project file for  reference  and remove the conflicts  If they re included in System  get rid of them  and  the build should work  This may not answer all cases of this issue - I m making sure you know what worked for me     Example of what I commented out    x000D   x000D   lt  --  lt Reference Include  System Runtime  Version 2 6 9 0  Culture neutral  PublicKeyToken b03f5f7f11d50a3a  processorArchitecture MSIL  gt  -- gt  x000D     lt  --  lt HintPath gt   SolutionDir packages Microsoft Bcl 1 1 9 lib net40 System Runtime dll lt  HintPath gt  -- gt  x000D     lt  --  lt Private gt True lt  Private gt  -- gt  x000D   lt  --  lt  Reference gt  -- gt  x000D   x000D   x000D

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I had this warning after migrating to Package Reference  In diagnostic output there was information that library was referenced by the same library itself  It might be a bug of new Package Reference  The solution was to enable AutoGenerateBindingRedirects and delete custom binding redirect

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You could run the Dotnet CLI with full diagnostic verbosity to help find the issue   dotnet run --verbosity diagnostic  gt  gt  full build log  Once the build is complete you can search through the log file  full build log  for the error  Searching for  a conflict  for example  should take you right to the problem

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and how do I then make the warning go away    You are probably going to have to reinstall or upgrade your NuGet packages to fix this

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I have uninstalled Microsoft ASP NET MVC nuget org from manage NuGet Packagaes and again re-installed it  While re-installing it resolved all the conflicts related to razor version  Try it

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Obviously there s a lot of different causes and thus a lot of solutions for this problem  To throw mine into the mix  we upgraded an assembly  System Net Http  that was previously directly referenced in our Web project to a version managed by NuGet  This removed the direct reference within that project  but our Test project still contained the direct reference  Upgrading both projects to use the NuGet-managed assembly resolved the issue

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I just ran into this and the problem after switching a package from nuget to locally referenced dlls  The issue was old runtime binding stuff in app config

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Please note that I solved this problem by putting the AutoGenerateBindingRedirects right after the TargetFramework in the csproj file   lt TargetFramework gt net462 lt  TargetFramework gt   lt AutoGenerateBindingRedirects gt true lt  AutoGenerateBindingRedirects gt

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I followed the advice of several of the responses here to figure out what was wrong  but none of the answers seemed to explain how to fix it  My issue was that one reference required a different version of a second reference  So Newtonsoft was at version 6  but some other DLL wanted 4 5  Then I upgraded Newtonsoft as one of the other answers suggested and that made things worse   So I actually downgraded my Newtonsoft install and the warning went away  VS 2017    Right click References in the solution explorer and select Manage NuGet Packages    Under the  Installed  tab  find Newtonsoft  or whatever your conflict is  On the right side  a dropdown appears next to  Version  that you can change to older versions  It wasn t obvious to me that this dropdown could be used to downgrade

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I can only support further Ruben s answer with a comparison between the two messages displayed     and the message      C  Program Files  x86  MSBuild 12 0 bin Microsoft Common CurrentVersion targets 1697 5   warning MSB3277  Found conflicts between different versions of the same dependent assembly that could not be resolved   These reference conflicts are listed in the build log when log verbosity is set to detailed    So  Ruben s right   this is just not true  There are no conflicts whatsoever  just a missing assembly  This is especially boring when the project is an ASP NET application  since the views are compiled on demand  that is  just before displayed for the first time  This is when it becomes necessary to have the assembly available   There s an option to pre-compile the views together with the rest of the code  but this is another story   On the other hand  if you set the verbosity to Diagnostic you get the following output      C  Program Files  x86  MSBuild 12 0 bin Microsoft Common CurrentVersion targets 1697 5   warning MSB3245  Could not resolve this reference  Could not locate the assembly  System Web Razor  Version 3 0 0 0  Culture neutral  PublicKeyToken 31bf3856ad364e35  processorArchitecture MSIL   Check to make sure the assembly exists on disk  If this reference is required by your code  you may get compilation errors    As a result  all you need to do is either    Add a reference to the assembly manually  locate it on disk  maybe GAC  and add it as a  direct  reference   or   Use NuGet package  if published in the gallery  to download it and reference the assembly contained within it    More about NuGet gallery here   More about precompiling ASP NET views here

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eta  There s a killer article on this stuff by SO s own  Nick Craver that you should read  While the other responses say this  they don t make it explicit  so I will     On VS2013 2  to actually trigger the emission of the cited information  you need to not read the message  which says   C  Program Files  x86  MSBuild 12 0 bin Microsoft Common CurrentVersion targets 1697 5   warning MSB3277  Found conflicts between different versions of the same dependent assembly that could not be resolved   These reference conflicts are listed in the build log when log verbosity is set to detailed   This is incorrect  or at least it was for some versions of Visual Studio - it seems to be OK on an up to date VS2015 Update 3 or later   Instead turn it to Diagnostic  from Tools- gt Options- gt Project and Solutions- gt Build and Run  set MSBuild project build output verbosity   whereupon you ll see messages such as   There was a conflict between  quot Newtonsoft Json  Version 6 0 0 0  Culture neutral  PublicKeyToken 30ad4fe6b2a6aeed quot  and  quot Newtonsoft Json  Version 6 0 5 17707  Culture neutral  PublicKeyToken 30ad4fe6b2a6aeed quot     quot Newtonsoft Json  Version 6 0 0 0  Culture neutral  PublicKeyToken 30ad4fe6b2a6aeed quot  was chosen because it was primary and  quot Newtonsoft Json  Version 6 0 5 17707  Culture neutral  PublicKeyToken 30ad4fe6b2a6aeed quot  was not    Then  Ctrl-Alt-O to go to Build output window search for  quot was chosen quot  to find the drilldown      And yes  for those looking at the detail of the  diagnostic  message  it was news to this ignoramus that there s a convention in town whereby all 6 x versions are  internally Assembly Version 6 0 0 0  i e  only the SemVer Major component goes into the Assembly Version

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Run msbuild Foo sln  t Rebuild  v diag  from C  Program Files  x86  MSBuild 12 0 bin  to build your solution from command line and get a bit more details  then find the  csproj  that logs the warning and check its references and references of other projects that use the same common assembly that differs in version   Edit  You can also set the build verbosity directly in VS2013  Go to Tools   Options menu then go to Projects and Solutions and set MSBuild verbosity to Diagnostic   Edit  Few clarifications as I just got one myself  In my case warning was due to me adding a reference using Resharper prompt as opposed to the Add Reference dialog  which did it versionless even though both v4 and v12 are available to choose from    lt Reference Include  Microsoft Build  Version 12 0 0 0         gt   lt Reference Include  Microsoft Build Framework    gt    vs   lt Reference Include  Microsoft Build  Version 12 0 0 0         gt   lt Reference Include  Microsoft Build Framework  Version 12 0 0 0         gt    In the MSBuild log with  v diag verbosity it looked like the following  giving details which two references conflicted -    There was a conflict between     Microsoft Build Framework  Version 4 0 0 0       and     Microsoft Build Framework  Version 12 0 0 0         TaskId 16          Microsoft Build Framework  Version 4 0 0 0       was chosen because it was primary and         Microsoft Build Framework  Version 12 0 0 0       was not   TaskId 16         References which depend on  Microsoft Build Framework  Version 4 0 0 0               C      v4 5 1 Microsoft Build Framework dll    TaskId 16             C      v4 5 1 Microsoft Build Framework dll  TaskId 16              Project file item includes which caused reference  C      v4 5 1 Microsoft Build Framework dll    TaskId 16                Microsoft Build Framework  TaskId 16         References which depend on  Microsoft Build Framework  Version 12 0 0 0               C      v12 0 Microsoft Build Framework dll    TaskId 16             C      v12 0 Microsoft Build dll  TaskId 16              Project file item includes which caused reference  C      v12 0 Microsoft Build dll    TaskId 16                Microsoft Build  Version 12 0 0 0       TaskId 16             C      v12 0 Microsoft Build Engine dll  TaskId 16              Project file item includes which caused reference  C      v12 0 Microsoft Build Engine dll    TaskId 16                Microsoft Build  Version 12 0 0 0       TaskId 16   C  Program Files  x86  MSBuild 12 0 bin Microsoft Common CurrentVersion targets 1697 5   warning MSB3277   Found conflicts between different versions of the same dependent assembly that could not be resolved    These reference conflicts are listed in the build log when log verbosity is set to detailed    C  Users Ilya Kozhevnikov Dropbox BuildTree BuildTree BuildTree csproj

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If you made any changes to packages -- reopen the sln  This worked for me

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I changed the  MSBuild verbosity to Diagnostic but couldn t find where the problem was so according to the answers above I had this code in app config    lt  xml version  1 0  encoding  utf-8   gt   lt configuration gt   lt configSections gt   lt section name  log4net  type  log4net Config Log4NetConfigurationSectionHandler  log4net    gt   lt sectionGroup name  userSettings  type  System Configuration UserSettingsGroup  System  Version 12 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089  gt   lt section name  XbimXplorer Properties Settings  type  System Configuration ClientSettingsSection  System  Version 4 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089  allowExeDefinition  MachineToLocalUser  requirePermission  false    gt   lt  sectionGroup gt   lt  configSections gt   lt startup gt   lt supportedRuntime version  v4 0  sku   NETFramework Version v4 5    gt   lt  startup gt    So I just changed the first System  Version from 4 0 0 0 to 12 0 0 0 and my project worked

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As per the other answers  set the output logging level to detailed and search there for conflicts  that will tell you where to look next   In my case  it sent me off in a few directions looking for the source of the references  but in the end it turned out that the problem was one of my portable class library projects  it was targeting the wrong version and was pulling its own version of the references in  hence the conflicts  A quick re-target and the problem was solved

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Run Update-Package command via Package Manager Console  This will fix MSB3277  what it does it reinstall all the packages and all related assemblies they come with to the highest version possible  It is also possible to update just specific package  Or downgrade after update if wanted  this fixed issue for me few times it came up  Depending on how many nuget packages you have  this process may take few minutes   More info on official docs https   docs microsoft com en-us nuget consume-packages reinstalling-and-updating-packages

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Changing the build verbosity in visual studio will help to point in the right direction  Follow the below steps to change verbosity in VS   Go to Tools- Options menu in VS Open Projects and Solutions- Build and Run Change the value of the MSBuild project build output verbosity  Pick one from Quiet  Minimal  Normal  Detailed and Diagnostic   Check the output window Ctrl Alt O  in VS to see the changes in the build log

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VS 2017  MVC project  I don t know why  but for me  the solution for this issue was to remove an out parameter from a model method signature that was called from the controller action method  that is very strange behaviour but that was the solution to my problem

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As stated in dotnet CLI issue 6583 the issue should be solved with dotnet nuget locals --clear all command

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I could solve this installing Newtonsoft Json in the web project with nugget packages

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I m using Visual Studio 2017 and encountered this when I updated some Nuget packages  What worked for me was to open my web config file and find the  lt runtime gt  lt assemblyBinding gt  node and delete it  Save web config and rebuild the project   Look at the Error List window  You ll see what looks like a massively long warning about binding conflicts  Double-click it and it will automatically recreate the  lt runtime gt  lt assemblyBinding gt  block with the correct mappings

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Reiterating one of the comments from  elshev Right click on the solution -  Manage NuGet packages for solution -  Under Consolidate you can see if there are different versions of the same package was installed  Update the packages there  The conflict error is resolved

[.net] Found conflicts between different versions of the same dependent assembly that could not be resolved

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