Could not load file or assembly An attempt was made to load a program with an incorrect format System BadImageFormatException

Question

I have two projects  ProjectA and ProjectB   ProjectB is a console application  which depends on ProjectA   Yesterday  everything was working fine  but suddenly today when I run ProjectB I get this      BadImageFormatException was unhandled    Could not load file or assembly  ProjectA  Version 1 0 0 0  Culture neutral  PublicKeyToken null  or one of its dependencies  An attempt was made to load a program with an incorrect format    Both are just regular projects  with no dependencies on any other non- Net projects   Both are fully  Net - there is no native code  and no P Invoke   I have other projects which depend on ProjectA and still work just fine   Things I have tried    Make sure both projects are set to  Any CPU   with the build checkbox checked   They are  Make sure both projects are for the same Target Framework   Net 4 0 Client Profile   Under ProjectB --  References --  ProjectA --  Properties  make sure  Copy Local  is set to  True     I verified that ProjectA dll is being copied correctly  Clean Rebuild the solution   I even tried manually deleting the  bin and  obj folders in both projects  Restart Visual Studio   Restart my computer  Check out an entirely new copy of the repository    But I still get the same error   I have no idea what I did to cause this  nor how to fix it   Any ideas

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It can be a little funny  but I had the same problem with normal working code  I added StreamWriter and StreamReader and it gave that error  The solution was I took that code into comment brackets then did debug and it started to work again

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I encountered the same issue   It popped up out of the blue and that seemed strange to me   In the Exception snapshot  for the FusionLog  I saw the following within its message       C  Windows Microsoft NET Framework64      More about the fusion log  http   msdn microsoft com en-us library e74a18c4 v vs 110  aspx  All the projects had a Target CPU of AnyCPU   I changed the application project  the project that references all the other projects  to a Target CPU of x86   It now works   Not sure how the Target CPU mix up occurred for no apparent reason  but it did

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I also face this problem in a project  after a few minutes i found the solution   this problem is due to CPU configuration  If you are using Visual Studio 2010 or VS 2013  just goto project  s properties and then select Compile from side bar and there will be 5 drop-down  5th Drop-down will be Target CPU   you should set it to x86 or x64 according to your requirements instead of Any CPU    My problem was solved after changing it to x86

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I just had this error message running IIS Express in Visual Studio 2015  In my case I needed to be running the 64 bit version of IIS Express      Tools   Options   Projects and Solutions   Web Projects   Check the box   that says  Use the 64 bit version of IIS Express for web sites and   projects     Screenshot

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None of these solutions worked for me - but by deleting the contents of bin and obj folders everything was cool again

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In my case the error was System BadImageFormatException  Could not load file or assembly  vjslib  Version 2 0 0 0  Culture neutral  PublicKeyToken b03f5f7f11d50a3a  or one of its dependencies  It was solved by installing vjredist 64 from here

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I had the same issue  Project B in my case was a  Net Core Class Library which has a Nuget  Microsoft Management Infrastructure  installed  The error was that i called my project B  MI   I changed the project name to something else and suddenly everything worked again

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First of all I got this in VS2017 with an old project I needed to make a tiny change to and upraded all the projects to framework 4 7     Several others have mentioned selecting Any CPU can fix this issue   There s a couple places you need to do it  and it might not just be as simple as selecting from the dropdown  This fixed it for me   1  You need to do it both here     2  And also in Configuration Manager  right click on solution     But what if it isn t there     Then click New and choose these settings   thanks  RckLN

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I had this same problem  I had set Project A s  Platform Target    Project A  Right Click - Properties- Build-  Platform Target   to x86 but kept Project B s at  Any CPU   Setting Project B s to  x86  fixed this

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I also had this problem running unit tests by using ReSharper on Visual Studio 2017 and fixed it with following config     Also you can change the ReSharper s run test setting  https   resharper-support jetbrains com hc en-us articles 207242715-How-to-run-MSTest-tests-using-x64-configuration

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My machine showed me a BIOS update and I wondered if that has something to do with the sudden popping-up of this error  And after I did the update  the error was resolved and the solution built fine

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You may need to change the Appication Pool setting  Enable 32bit Applications  to TRUE in IIS7 if you have at least 1 32bit dll exe in your project

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This also can happen just by having multiple supported frameworks defined in the app config file and  forcing the app to run in a different  NET framework other than the one mentioned first in the app config file   And also this fires when you have both of the mentioned frameworks available in your system   As a workaround  bring up the target framework you are going to use for the debugging up in the app config  ex  if you trying to run in  NET 4  config file should have something similar to this    lt supportedRuntime version  v4 0   gt   lt supportedRuntime version  v2 0 50727   gt

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I am pretty sure you re having a 32-bit   64-bit conflict  It sounds like your main project might be set to 32-bit while the class its referencing is set to 64-bit  Try looking at this SO question and this one too  Between the two of them  you should be able to figure out your problem

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The following solved the issue for me  uncheck  Prefer  32-bit

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You might also see this issue if you re trying to package a 64bit project with an MSI installer in VS    The reason is because the native shim packaged with the  msi file is a 32-bit executable     See here for more details  http   blogs msdn com b heaths archive 2006 02 01 64-bit-managed-custom-actions-with-visual-studio aspx

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The Chilkat  NET 4 5 assembly requires the VC   2012 or 2013 runtime to be installed on any computer where your application runs  Most computers will already have it installed  Your development computer will have it because Visual Studio has been installed  However  if deploying to a computer where the required VC   runtime is not available  the above error will occur   Install all of the bellow packages  Visual C   Redistributable Packages for Visual Studio 2013 - vcredist x64  Visual C   Redistributable Packages for Visual Studio 2013 - vcredist x86  Visual C   Redistributable Packages for Visual Studio 2012 - vcredist x64  Visual C   Redistributable Packages for Visual Studio 2012 - vcredist x86

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In my case a dependency was missing in the dll that threw this exception  I checked with Dependency Walker  added the missing dll and the problem was resolved   More specifically  I somehow corrupted my opencv core340 dll by accidentally adding SVN keywords to it  and thus my dll could no longer use it  However I don t believe that the solution to this problem depends on whether the dll is corrupted or missing  I m just adding this for the sake of giving complete information

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In my project for C   project property-  Build - Platform target  Any CPU  and uncheck the Prefer 32-bit to let compiler to choose automatically

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Shoot  I knew about this problem  I thought I was doing everything right until I accidentally saw  x86  in the VS output window and that s when I got hold of the cause  Wasted a few mins on it today   The configuration under  Publish  window was set to  x86   whereas  everywhere else  it was  x64    Please make sure it s in-sync across configuration manager  publish settings  solution configurations  and IIS settings  if that s your web server     Also  please keep in mind - VS is a 32-bit app and IIS is 64 bit  32-bit apps are disabled by default in IIS

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If you use LibreOffice from your program via cli  net integration like me  I got the same error  I use the older version of LibreOffice on the production environment on my PC I installed a newer version that was in conflict  Just uninstall LibreOffice  I found the solution here  NET CLI  Could not load file or assembly  cli cppuhelper

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Are you trying to run your  exe file from the cmd  This was my mistake  Just run the  exe file by double clicking it  If it s a  NET Core SCD for Windows 8 1 Windows Server 2012 R2 x64

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Might be you are facing the problem with your website after deploying on server   Then you need to adjust your application pool to Enable 32-Bit Applications   Steps   Open IIS Manager Click on Application Pools Select whatever application pool you are using From right pane  click Advanced Settings    Set Enable 32-Bit Applications to True

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I have detected something different from the other answers  Reaching this exception in my project was the result of a corrupt compilation  Without making any changes  just forcing rebuild  it was fixed

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I got this when building a project via Visual Studio Online  VSTS  Build using Visual Studio Build Steps   The solution was    Delete the existing source folder Explicitly set  Any CPU  in the platform for all Visual Studio Builds including dependencies  see screenshot below   Re-run the build

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I had this problem running unit tests  xunit  in Visual Studio 2015 and came across the following fix   Menu Bar - gt  Test - gt  Test Settings - gt  Default Processor Architecture - gt  X64

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I had the same issue with multiple projects in the same solution  i ended up setting all of the target frameworks to  NET Framework 4 and x86 for the target CPU and it finally successfully compiled

[c#] Could not load file or assembly ... An attempt was made to load a program with an incorrect format (System.BadImageFormatException)

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