Error The type exists in both directories

Question

In a MVC2 project I moved a file from App code to Content folder and compiled it  Then move it back again to App Code and then changed its Build Action to  Compile   Now I get this error and I don t know how to fix this to make my program work again      CS0433  The type  Helper  exists in   both    c  Users    AppData Local Temp Temporary   ASP NET   Files root b00d4b7d b2553f9c App Code zowyklar dll    and    c  Users    AppData Local Temp Temporary   ASP NET   Files root b00d4b7d b2553f9c assembly dl3 5c6d3537 19f85663 cde9cb01 MyProject DLL    Cleaning and Rebuilding doesn t solve the problem

User · Answer

There might be two classes with same name  Helper  in your solution project  Change name of one of them and then rebuild

User · Answer

Another potential solution which worked for me was to change all references from  CodeFile           to  CodeBehind           in all  master and  aspx pages  This occurred when converting an old website to a proper web application with a solution file   I didn t find this information anywhere else so hope this helps someone

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Try cleaning your solution and then try to rebuild   Visual Studio probably still has reference to the old dll after it created the new dll

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My issue was with different version of DevExpress   Deleting all contents from bin and obj folders made my website run again     Reference  https   www devexpress com Support Center Question Details KA18674

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I fixed this by checking Delete all existing files prior to publish in Visual Studio

User · Answer

The App Code folder isn t intended to be used with MVC Projects  WAP    Files in the App Code folder gets compiled automatically as part of a special dll  If the Build Action property on the file is set to Compile  the same class will also get compiled as part of the main dll and you will end up with two copies   Setting the Build Action property to None makes sure there is only one copy of the class in the project  The compiler will not catch any errors in the App Code folder when building but Intellisense will still validate the code but compile-time errors won t show up until it is compiled on-the-fly   The recommended solution is to put code in a normal folder and make sure the Build Action is set to Compile

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I tried pretty much every suggestion on this page  but had to delete visual studio 2017 completely off my machine  I reinstalled the latest version  2019  and it magically worked  I hope this helps someone in the future

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I fixed this by removing one of the unneeded NuGet packaged referenced in the dll files causing this conflict  So in this case I had both ZXing Net and ZXing Net Mobile installed  Since I was creating a mobile app in Xamarin Forms  removing the ZXing Net NuGet package resolved this  Be sure to check and make sure you don t have redundant NuGet packages for different frameworks  i e  ASP Net versus Xamarin

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TRY THIS ONE   Normally  when this happen locally  i clean all the aspnet temp folder  But recently it was happing when i published my website in Azure  So  clean temp aspnet folder  was not a solution    After searching on the internet  i founded this   Clear Temp ASP NET files from Azure Web Site  It works for me

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This has been answered in a separate question and resolved the problem for me   Be sure to vote up the original person s answer   ASP Net error   quot The type   39 foo  39  exists in both  quot temp1 dll quot  and  quot temp2 dll quot   Add the batch  false  attribute to the  compilation  element of the web config file   This problem occurs because of the way in which ASP NET 2 0 uses the application references and the folder structure of the application to compile the application  If the batch property of the element in the web config file for the application is set to true  ASP NET 2 0 compiles each folder in the application into a separate assembly   http   www sellsbrothers com news showTopic aspx ixTopic 1995  http   support microsoft com kb 919284

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I had the same problem in one of my projects  Turns out the problem started from me coping a Master page   The problem will also occur if two pages  Inherit  the same page   I had the following line of code at the top of my  LoginMaster Master   amp   MasterPage Master    lt    Master Language  C   AutoEventWireup  true  CodeFile  MainMaster master cs  Inherits  Master Pages Header    gt    I changed the Inherits on my  LoginMaster Master to     lt    Master Language  C   AutoEventWireup  true  CodeFile  LoginMaster master cs  Inherits  Master Pages LoginMaster    gt    I was immediately able to publish my project with out any problems  Hopefully this works for someone else  I apologize for not use the correct terms   You will also need to change the class in the  cs to match the Inherits name  If you don t it will cause an error   IE    public partial class Master Pages LoginMaster   System Web UI MasterPage

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Simple Solution worked 100  for me  Put the class outside App Code Folder  http   vishaljoshi blogspot in 2009 07 appcode-folder-doesnt-work-with-web html

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Assuming you re building a Web Application  which it appears you are given the MVC2 point  you shouldn t use the App Code folder  It was not designed to be integrated with Web Application projects      When you Compile in Visual Studio  all the code in your application    including in App Code  gets compiled into an assembly  When you run   your application  asp net knows about a  special  folder called   App Code and compiles the content of it into an assembly with a unique   name  Thus  anytime you run the project you ll run into this problem    The solution      Rename your App Code folder to something like  Code  or  Global     and update your now broken references   amp  voila  problem solved

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In the Web Application not Web Site    I change App Code  cs Build Action file properties  from Compile to Content  then the problem solve

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In my case  I have to items with same name but different extensions in my project  One was accountRep aspx and the other accountRep rpt made by Crystal Report  Problem solved when I changed accountRep rpt to accountReport rpt

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I had the same error   The type  MyCustomDerivedFactory  exists in both  and  My ServiceHost and ServiceHostFactory derived classes where in the App Code folder of my WCF service project  Adding   lt configuration gt     lt system web gt       lt compilation batch  false    gt     lt  system web gt   lt configuration gt    didn t solve the error but moving my ServiceHost and ServiceHostFactory derived classes in a separate Class library project did it

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In my case I got this error when I had mistakenly named a class the same as the class it was inheriting from

User · Answer

Try to change folder name  from APP CODE to CODE   This fixed my issue  Alternatively you can move to another folder all your code files

User · Answer

If your are migrating ASP NET 2 0 Website to  NET Web APP 4 5  you can have that issue too  And puting batch false  adding a namespace etc    can not work    The workaround is to rename the old App Code folder  or any problematic folder  to Old App Code  like the automatic process do it   or any other name

[asp.net] Error: The type exists in both directories

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