Summary of your issue

Getting OpenCvSharp4.Windows from nuget, try demo code of lenna, got this error

System.TypeInitializationException
  HResult=0x80131534
  Message=The type initializer for 'OpenCvSharp.NativeMethods' threw an exception.
  Source=OpenCvSharp
  StackTrace:
   at OpenCvSharp.NativeMethods.imgcodecs_imread(String filename, Int32 flags)
   at OpenCvSharp.Mat..ctor(String fileName, ImreadModes flags)
   at OpenCvSharpYolo3.Program.Main(String[] args) in D:\Users\Died.Liu\source\repos\OpenCvSharpYolo3\OpenCvSharpYolo3\Program.cs:line 14

Inner Exception 1:
DllNotFoundException: Unable to load DLL 'OpenCvSharpExtern': The specified module could not be found. (Exception from HRESULT: 0x8007007E)

Environment

package id=“OpenCvSharp4.Windows” version=“4.0.0.20181225” targetFramework=“net46” win 10 v1809 , vs2017 v18.8.9

What did you do when you faced the problem?

the demo code work on OpenCvSharp v3, it should be work at v4

Example code:

demo code

Quick fix

stupid way copy dll folder from previous project that using OpenCvSharp3. put into your \bin\debug then it work, but I think it’s for v3 not v4.

Guess

Maybe it’s typo or something, @shimat can you check it ?

I noticed on frontpage ubuntu build Instructions have Build native wrapper OpenCvSharpExtern, so I think it maybe miss on OpenCvSharp4.Windows nuget package, it didn’t include OpenCvSharpExtern.dll,