How do I resolve Please make sure that the file is accessible and that it is a valid assembly or COM component

Question

I am building a project with OpenCV in C   It requires a dll file called cvextern dll  but  when adding this file as a reference  this message appears  -  a reference  cvextern dll  can t be added  Please make sure that the file is accessible and that it is a valid assembly or COM component   I get tired from searching  I spent the past 2 days in searching for a solution for that problem

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In my case I also have unmanaged dll s  C    in workspace and if you specify    lt files gt       lt file src  bin   dll  target  lib    gt   lt  files gt    nuget would try to load every dll as an assembly  even the C   libraries  To avoid this behaviour explicitly define your C  assemblies with references tag    lt references gt       lt reference file  Managed1 dll    gt       lt reference file  Managed2 dll    gt   lt  references gt    Remark  parent of references is metadata -  according to documentation https   docs microsoft com en-us nuget reference nuspec general-form-and-schema  Documentation  https   docs microsoft com en-us nuget reference nuspec

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Make sure the required dlls are exported  or copied manually  to the bin folder when building your application

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Look here for the answer by TheMattster  I implemented it and it worked like a charm  In a nutshell  his solution suggests to add the COM dll as a resource to the project  so now it compiles into the project s dll   and upon the first run write it to a file  i e  the dll file I wanted there in the first place    The following is taken from his answer   Step 1  Add the DLL as a resource  below as  Resources DllFile    To do this open project properties  select the resources tab  select  add existing file  and add the DLL as a resource   Step 2  Add the name of the DLL as a string resource  below as  Resources DllName     Step 3  Add this code to your main form-load    if   File Exists Properties Resources DllName         var outStream   new StreamWriter Properties Resources DllName  false       var binStream   new BinaryWriter outStream BaseStream       binStream Write Properties Resources DllFile       binStream Close        My problem was that not only I had to use the COM dll in my project  I also had to deploy it with my app using ClickOnce  and without being able to add reference to it in my project the above solution is practically the only one that worked

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I had the same program  I hope this could help   I your using Windows 7  open Command Prompt-  run as Administrator   register your  lt      dll     Why run as Administrator  you can register your  lt      dll using the run at the Windows Start  but still your dll only run as user even your account is administrator   Now you can add your  lt      dll at the Project- Add Reference- Browse  Thanks

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the file is a native DLL which means you can t add it to a  NET project via Add Reference    you can use it via DllImport  see http   msdn microsoft com en-us library system runtime interopservices dllimportattribute aspx

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It  requires a dll file called cvextern dll    It  can be either your own cs file or some other third party dll which you are using in your project   To call native dlls to your own cs file  copy the dll into your project s root lib directory and add it as an existing item   Add -Existing item  and use Dllimport with correct location   For third party    copy the native library to the folder where the third party library resides and add it as an existing item   After building make sure that the required dlls are appearing in Build folder  In some cases it may not appear or get replaced in Build folder  Delete the Build folder manually and build again

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In my case I had to register the  dll   To do so  open cmd exe  the console  with admin rights and type   regsvr32  foo dll

[c#] How do I resolve "Please make sure that the file is accessible and that it is a valid assembly or COM component"?

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