The CodeDom provider type Microsoft CodeDom Providers DotNetCompilerPlatform CSharpCodeProvider could not be located

Question

It s a WebApi project using VS2015   Step to reproduce     Create an empty WebApi project Change Build output path from  bin   to  bin Debug   Run     Everything is working perfectly until I changed Build Output path from  bin   to  bin Debug    In fact  any Output path other than  bin   won t work   One little additional thing is that  having another output path to anywhere would work as long as I left a build in  bin      Please help providing solution to solve this   I guess that ll cost problem on actual deployment

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Be careful of following this answer s advice  While it solves the problem at hand  it might cause different problems at a later date    I got the same problem  Apparently the  NET compiler was not loaded to the GAC  What I did to solve it was   First  in the package manager console type   PM gt  Install-Package Microsoft CodeDom Providers DotNetCompilerPlatform   Now  for some reason the nice gentlemen in Microsoft have decided not to install it to the GAC for us  You can do it manually by opening the Developer Command Prompt and typing   gacutil -i  C   PATH TO YOUR APP CODE  bin Microsoft CodeDom Providers DotNetCompilerPlatform dll    Conclusion  Microsoft try to encourage everyone to do everything with nugets which could be fine without the occasional bugs you run into with the nuget system  Try to use the same project on different solutions  accidentally  or not  update one of the many nugets it uses on one of them  and if you are unlucky you ll see what I mean when you  try to build the other solution  On the other hand  putting files in the GAC can also cause future problems since people tend to forget what they put there and then when setting up new environments they forget to include these files  Another possible solution is to put the files in a central folder for 3rd party dlls  even though it s strange to call the compiler 3rd party   which creates problems of broken references when setting up new environments  If you decide to install the dll to the GAC  use caution and remember that you did so  If you don t  download the nuget for each project again and bear all the annoying bugs being caused by it  at least used to happen when I finally got sick of it and just placed the files in the GAC   Both approaches might give you headaches and create problems  it s just a question of which problems you prefer to deal with  Microsoft recommends to use the nuget system  and generally  it s better to listen to them than to an unknown programmer in SO  unless you are completely sick of the nuget system and used to deal with the GAC long enough for it to be a better alternative for you

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If you see this probably you are building in release mode  For production you should publish instead of building in release mode  For local development build in debug mode

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I was getting this error because my application pool user was set to ApplicationPoolIdentity  I changed it to a user service account that has access to the folder and the error went away

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ASP NET does not search bin debug or any subfolder under bin for assemblies like other types of applications do  You can instruct the runtime to look in a different place using the following configuration    lt configuration gt      lt runtime gt            lt assemblyBinding xmlns  urn schemas-microsoft-com asm v1  gt            lt probing privatePath  bin bin Debug bin Release   gt         lt  assemblyBinding gt      lt  runtime gt      lt  configuration gt

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I know it s an old thread  but I d like to point the possible version issue of DotNetCompilerPlatform dll  f  ex  after an update  Please check  if the new generated Web config file is different as your released web config  in particular the system codedom part  In my case it was the version change from 1 0 7 to 1 0 8  The new dll had been already copied to the server  but I didn t change the old web config  with some server special settings     lt pre gt     lt system codedom gt       lt compilers gt         lt compiler language  c  cs csharp  extension   cs  type  Microsoft CodeDom Providers DotNetCompilerPlatform CSharpCodeProvider  Microsoft CodeDom Providers DotNetCompilerPlatform  Version 1 0 8 0  Culture neutral  PublicKeyToken 31bf3856ad364e35  warningLevel  4  compilerOptions   langversion default  nowarn 1659 1699 1701    gt         lt compiler language  vb vbs visualbasic vbscript  extension   vb  type  Microsoft CodeDom Providers DotNetCompilerPlatform VBCodeProvider  Microsoft CodeDom Providers DotNetCompilerPlatform  Version 1 0 8 0  Culture neutral  PublicKeyToken 31bf3856ad364e35  warningLevel  4  compilerOptions   langversion default  nowarn 41008  define  MYTYPE   amp quot Web  amp quot   optionInfer     gt       lt  compilers gt     lt  system codedom gt   lt  pre gt    After I update the two lines  the error disappeared

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In our case we are using ToroiseSVN and it seems by default the bin folder is not added to the sourcecontrol  So when updating the website on the production server the bin folder was not added to it  thus resulting in this exception  To add the bin folder to SVN go to the folder on the hdd and find the bin folder  Right click it and select TortoiseSVN -- gt  Add Now update the repository to include the newly added files and update the production server next  All should be well now

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Easy way - Project   Manage NuGet Packages      Browse tab    in search input set this  Microsoft CodeDom Providers DotNetCompilerPlatform  You can install or update or uninstall and install this compiler

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The exception that we ran into was not on the local but on the remote server  the Azure CI was reading it from the packages folder but the compiler versions mentioned above were not found   To fix this we modified the project file to make it something like        It is not referencing any of the packages here directly referencing the environment variables   This fixed the issue  however in our cases we don t use packages directly from  package config  instead we have a separate folder to maintain version integrity across teams

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just uninstall the package from package manager console from command below  PM  Uninstall-package Microsoft CodeDom Providers DotNetCompilerPlatform  PM  Uninstall-package Microsoft Net Compilers  and then install it again from nuget manager

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In My case my web project was not loaded properly   it was showing project unavailable   then I had to reload my web project after opening my visual studio in admin mode then everything worked fine

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I had a number of projects in the solution and the web project  problem giving this error  was not set as the StartUp project  I set this web project as the StartUp project  and clicked on the menu item  Debug -  Start Debugging  and it worked  I stopped debugging and then tried it again and now it   s back working  Weird

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Check whether the BIN folder is uploaded completely or missing in the files

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Then the problem came back  I uninstalled both Microsoft CodeDom Providers DotNetCompilerPlatform and  Uninstall-package Microsoft Net Compilers but no help  Then installed - no help  Cleaned project and built no help  Restarted server no help Then I noticed the project needed not the latest one which is currently 1 0 5 but 1 0 3 as that was the error could not load the 1 0 3 version  So I installed that dll version instead and now it works

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Go to  inetmgr from start command In IIS manager console choose the application folder under Default Web Site right click on that folder then  Convert to Application Run the  asmx file by Enabling  It solved the problem

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According to your repro steps  I assumed that changing the output path in the application s property was your only change after you created the application  The only thing this change does is that it tells Visual Studio to put the output assemblies of MSBuild into the new folder  At runtime  however  ASP Net wouldn t have any idea that it should load assemblies from this new folder instead of the  bin folder    This answer shows the way to change the build output directory of a WebApi application  To get the exact same error showed in that post  you need to comment out the entire  lt system codedom gt  section in web config  And then you can follow the instructions to change the output path   After you get your applicaiton work  you may then uncomment the  lt system codedom gt  section  If you don t use C  6 new syntax in your application at all you can uninstall the Microsoft CodeDom Providers DotNetCompilerPlatform from you application  otherwise  you may want to add the following command line in your post-build event   xcopy  Q  Y    TargetDir roslyn         TargetDir    roslyn     The new CodeDom provider always looks for the   roslyn  folder in  bin  The above command works as a workaround and copies the  roslyn folder from your new output folder to  bin    In my experiments  the publish tool of Visual Studio  however  published the output assemblies to the  bin folder in the deployment location regardless my output path setting  I guess your application should still work on actual deployment

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I just had the same problem and it was because I moved the project location and simply needed to recreate the virtual directory

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Ensure Internet Information Services IIS  is enabled in Windows features on your machine

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You should update the  Microsoft CodeDom Providers DotNetCompilerPlatform  and  Microsoft Net Compilers  packages in your project

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If you have recently installed or updated the Microsoft CodeDom Providers DotNetCompilerPlatform package  double-check that the versions of that package referenced in your project point to the correct  and same  version of that package    In ProjectName csproj  ensure that an  lt Import gt  tag for Microsoft CodeDom Providers DotNetCompilerPlatform is present and points to the correct version  In ProjectName csproj  ensure that a  lt Reference gt  tag for Microsoft CodeDom Providers DotNetCompilerPlatform is present  and points to the correct version  both in the Include attribute and the child  lt HintPath gt   In that project s web config  ensure that the  lt system codedom gt  tag is present  and that its child  lt compiler gt  tags have the same version in their type attribute    For some reason  in my case an upgrade of this package from 1 0 5 to 1 0 8 caused the  lt Reference gt  tag in the csproj to have its Include pointing to the old version 1 0 5 0  which I had deleted after upgrading the package   but everything else was pointing to the new and correct version 1 0 8 0

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I have the same problem that my app worked in Vs2013 but getting the error after updating to Vs2015    In Vs2015  right click project s References folder  to open NuGet Package Manager Under Browse tab  search for  DotNetCompilerPlatform  and install  Microsoft CodeDom Providers DotNetCompilerPlatform  lib

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It stopped after publishing on the production server   The reason why it showed me this error was because it was deployed to a subfolder  In IIS i clicked right on the subfolder and excuted  Convert to application  and after this it worked

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Another possible solution    Restart your Visual Studio Instance with Administrator Rights

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Make sure your project has fully built  Click on  Output  tab and make sure you don t have something like              Rebuild All  14 succeeded  1 failed  0 skipped            And open your bin folder and check to see if it s up to date  I had a whole bunch of typescript errors that I ignored at first  forgetting that they were breaking the build and leading to there being no DLLs copied in

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Regarding this error I ve tried    Cleaning and rebuilding the project Unloading and reloading the project Modifying the Target Framework Modifying the Output path Adding nuggets to the GAC Deleting the packages uninstall-package Microsoft CodeDom Providers DotNetCompilerPlatform uninstall-package Microsoft Net Compilers and installing them again    While these all seem to be valid solutions  I was only able to generate new errors and in the end  the error seems able to display when certain references nugets are missing   In my case  I had recently reinstalled Microsoft Office and was referencing assemblies like Microsoft Office Core  The new install didn t seem to include the required packages  which made it so my solution couldn t build correctly   I was able to solve this issue by reworking my code to the point where I didn t need to reference Microsoft Office  but could ve solved it by looking up the required packages and installing them accordingly   Seems like an unclear error message from Visual Studio

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Here s how I resolved it                   Deleted the bin folder in the project directory  Click on Build Solution  In VS2017 Run as Admin    Build   Build Solution

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If your project has Roslyn references and you are deploying it on an IIS server  you might get unwanted errors on the website as many hosting providers still have not upgraded their servers and hence do not support Roslyn   To resolve this issue  you will need to remove the Roslyn compiler from the project template  Removing Roslyn shouldn t affect your code s functionality  It worked fine for me and some other projects  C  4 5 2  on which I worked   Do the following steps    Remove from following Nuget Packages using command line shown below  or you can use GUI of Nuget Package manager by Right Clicking on Root Project Solution and removing them    PM gt  Uninstall-package Microsoft CodeDom Providers DotNetCompilerPlatform PM gt  Uninstall-package Microsoft Net Compilers  Remove the following code from your Web Config file and restart IIS   Use this method only if step 1 doesn t solve your problem     lt system codedom gt   lt compilers gt     lt compiler language  c  cs csharp  extension   cs  type  Microsoft CodeDom Providers DotNetCompilerPlatform CSharpCodeProvider  Microsoft CodeDom Providers DotNetCompilerPlatform  Version 1 0 0 0  Culture neutral  PublicKeyToken 31bf3856ad364e35  warningLevel  4  compilerOptions   langversion 6  nowarn 1659 1699 1701    gt     lt compiler language  vb vbs visualbasic vbscript  extension   vb  type  Microsoft CodeDom Providers DotNetCompilerPlatform VBCodeProvider  Microsoft CodeDom Providers DotNetCompilerPlatform  Version 1 0 0 0  Culture neutral  PublicKeyToken 31bf3856ad364e35  warningLevel  4  compilerOptions   langversion 14  nowarn 41008  define  MYTYPE   amp quot Web  amp quot   optionInfer     gt   lt  compilers gt

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Just add the next nuget package to your project - Microsoft CodeDom Providers DotNetCompilerPlatform   Had the same problem

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Here are my findings  I also faced this problem today s morning  I just added my current user to application pool on which application was running   Steps    Open IIS Click on application pool Select your application pool on which you are getting problem Right Click -  advanced settings Click on three dot icon beside the identiy Now select custom account Give your PC user name and Password Save   Refresh your application   and it will start working  There was some security issue for accessing dll

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If you are using git  you are probably ignoring the  dll in the commit

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If you have been working on a project and this just now popped up as an error  REBOOT your computer  or server in my case  this fixed the issue for me

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Add a reference to the CppCodeProvider assembly

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In my case  this happened when i change the permission of application folder and account IIS IUSRS has been removed  After i re-added IIS IUSRS  IIS Manager-  YourWebApp -  Edit Permission -  Add IIS IUSRS  to the application folder and its worked

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In my case  I got the error when I had my Web Application in 4 5 2 and the referenced class libaries in 4 6 1  When  I updated the Web Application to 4 5 2 version the error went away

[c#] The CodeDom provider type "Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider" could not be located

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