Could not load file or assembly Oracle DataAccess or one of its dependencies

Question

I am trying to run this web application  I keep getting this error  Could not load file or assembly  Oracle DataAccess  or one of its dependencies  An attempt was made to load a program with an incorrect format   Exception details  System BadImageFormatException   Could not load file or assembly  Oracle DataAccess  or one of its dependencies  An attempt was made to load a program with an incorrect format   Below are the things that I already tried   1  replaced all the oracle dll s with 32 bit oracle dll i e 2 112 3 0  I have 32 bit client installed on 64 bit machine  The operating system is windows 7   2  compile each individual project individually  Deleted all the oracle dependent files dll and then added the 2 112 3 0 dll s individually and then compiled each project  3  Register the 32 bit dll on GAC using this statement  gacutil  i  ORA HOME4  odp net bin 4 Oracle DataAccess dll  gacutil  i  ORA HOME4  asp net bin 4 oracle web dll  for the above two statements  I copied the gacutil exe from c  Program Files x86  Microsoft sdk windows v7 0A Bin NETFX4 0 Tools X64 to C   drive and then  I executed the above two statement   gacutil  i  ORA HOME4  odp net bin 4 Oracle DataAccess dll gacutil  i  ORA HOME4  asp net bin 4 oracle web dll when I executed the above two statements  I didn t get any message  I executed them in Dos windows under administrator privilege   4  I also deleted all the Temporary ASP net files from this location  c  windows Microsoft Net V4 0 30319 temporary ASP net files I also changed the web application build Platform target to X86  Originally  it was at  ANy CPU   out of frustration  I also tried changing the platform target to X64 and then I got the error message saying    Cold not load file or assemble   webapp  or one of its dependencies  An attempt was made to load a program with an incorrect format   I don t have IIS installed on my computer  I am running this application in visual studio 2010 so I think it will be using the inbuilt IIS that comes with visual studio   I spend lot of hours resolving this issue  but still getting the same error again and again   any help or hint will be highly appreciated

User · Answer

I found the solution with following steps:

remove the Oracle.DataAcces.dll reference,
and add a fresh reference to:
C:\windows\assembly\GAC\Oracle.DataAccess\X.XXX.X.XX__89b483f429c47342/oracle.dataaccess.dll
Make local copy= false.

Hope it helps

User · Answer

Had the issue again when i moved from one machine to another and had everything reinstalled  In my case  i m using both 32bit and 64bit Oracle ODP NET installs   When listing the assemblies on my new machine i ended up with the following list   C  oracle product 11 2 0 X64 odp net bin 4 gt gacutil  l findstr Oracle DataAccess      Oracle DataAccess  Version 2 112 3 0  Culture neutral  PublicKeyToken 89b483f429c47342  processorArchitecture AMD64      Policy 2 102 Oracle DataAccess  Version 2 112 3 0  Culture neutral  PublicKeyToken 89b483f429c47342  processorArchitecture AMD64      Policy 2 111 Oracle DataAccess  Version 2 112 3 0  Culture neutral  PublicKeyToken 89b483f429c47342  processorArchitecture AMD64      Policy 2 112 Oracle DataAccess  Version 2 112 3 0  Culture neutral  PublicKeyToken 89b483f429c47342  processorArchitecture AMD64      Oracle DataAccess  Version 4 112 3 0  Culture neutral  PublicKeyToken 89b483f429c47342  processorArchitecture AMD64      Policy 4 112 Oracle DataAccess  Version 4 112 3 0  Culture neutral  PublicKeyToken 89b483f429c47342  processorArchitecture AMD64   only 64bit DLLs to be seen here     I couldn t see it from the web config but the one i was using was a 32bit version   When checking my old machine with the GACutil  i saw more DLLs  also the X86 ones   Fixed by reapplying the registration process both x32 x64 version referenced here   OraProvCfg exe  action gac  providerpath C  oracle product 11 2 0 x32 ODP NET bin 4 Oracle DataAccess dll  OraProvCfg exe  action gac  providerpath C  oracle product 11 2 0 x64 ODP NET bin 4 Oracle DataAccess dll   after that   Visual Studio was a happy bunny and compiled everything again for me

User · Answer

Try this  Open IIS Manager  change application pool s advance setting  change Enable 32 bit Application to false

User · Answer

If you are using IIS Express and VS 2017   Go to the Web Application Properties   Web Tab   Servers Section   And change the Bitness to x64

User · Answer

In my case the following solved the problem    Downloading the  32-bit Oracle Data Access Components  ODAC   with Oracle Developer Tools for Visual Studio  from http   www oracle com technetwork topics dotnet utilsoft-086879 html Then adding reference oracle dataaccess dll to the bin file by browsing the file location or just from the refence list in  NET tab

User · Answer

I needed a 64-bit version of oracle dataaccess dll but this caused problems with other libraries I was using       BadImageFormatException  Could not load file or assembly  Oracle DataAccess  or one of its dependencies  An attempt was made to load a program with an incorrect format     I followed several steps above  Going to advance settings on the projects pool to toggle allow 32bit worked but I wasn t content to leave it like that so i turned it back on   My project also had references that relied on Elmah and log4net references   I downloaded the latest version of these and my project was able to build and run fine without messing with the pools s allow 32bit setting

User · Answer

In my case  I use VS 2010  Oracle v11 64 bits  I might to publish in 64 bit mode  Setting to  Any Cpu  mode in Web Project configuration  and I might set IIS on Production Server to 32 Bit compability to false  because the the server is 64 bit and I like to take advantage it    Then to solve the problem  Could not load file or assembly  Oracle DataAccess       In the Local PC and Server is installed Oracle v11  64 Bit  In all Local Dev PC I reference to Oracle DataAccess dll  C  app user product 11 2 0 client 1 odp net bin 4  which is 64 bit     In IIS Production Server  I set 32 bit compatibility to False  The reference in the web project at System Web Mvc dll was the version v3 0 0 1 in the local PC  however in Production is only instaled MVC version 3 0 0 0  So  the fix was locallly work with MVC 3 0 0 0 and not 3 0 0 1 and publish again on server  and it works

User · Answer

I had the same error with Oracle DataAccess but deploying to Azure Web Sites  azurewebsites net   For me I had to edit a setting in VS NET 2019 before publishing to Azure  I ticked the checkbox   Use the 64 bit version of IIS Express for Web sites and projects  which is found under Tools  gt  Options  gt  Projects and Solutions  gt  Web Projects

User · Answer

For me everything else was almost ok  but somehow my project settings changed  amp  iisExpress was getting used instead of IISLocal  When I changed  amp  pointed to the virtual directory  in IISLocal   it stared working perfectly again

User · Answer

i Have face the same issue and resolved by replacing the old Oracle DataAccess dll with new Oracle DataAccess dll which come with oracle client when install   in my case the path of  new Oracle DataAccess dll is     E  app Rehman Rashid product 11 2 0 client 1 ODP NET bin

User · Answer

You may need to enable 32-bit applications in your AppPool   Go to    Application Pool  in IIS    right click your app pool    advance setting     enable 32 bit application  to true    Please don t forget to restart your app pool and your corresponding application pointing to that app pool

User · Answer

In my case I had a console application  I just unchecked Prefer 32-bit on Build projet properties tab and then I add this to my app config   lt runtime gt           lt assemblyBinding xmlns  quot urn schemas-microsoft-com asm v1 quot  gt               lt dependentAssembly gt                   lt assemblyIdentity name  quot Oracle DataAccess quot  publicKeyToken  quot 89b483f429c47342 quot  culture  quot neutral quot    gt                   lt bindingRedirect oldVersion  quot 0 0 0 0-5 0 0 0 quot  newVersion  quot 2 112 1 0 quot    gt               lt  dependentAssembly gt           lt  assemblyBinding gt       lt  runtime gt

User · Answer

Also you can download and execute the install bat file in  ODAC112030Xcopy zip  from 64-bit Oracle Data Access Components  ODAC  Downloads  This resolved my problem

[visual-studio-2010] Could not load file or assembly "Oracle.DataAccess" or one of its dependencies

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