Summary of your issue

Using VSCode and dot net core 2.2 following the instructions 👍

dotnet new console -n ConsoleApp01
cd ConsoleApp01
dotnet add package OpenCvSharp4
dotnet add package OpenCvSharp4.runtime.ubuntu.18.04-x64

-- edit Program.cs ---

dotnet run

When I add the following code

using System;
using OpenCvSharp;

namespace ConsoleApp01
{
class Program
{
static void Main(string[] args)
{
var srcImage = new Mat(@"/somepathtoafile.jpg");
Cv2.ImShow("Source", srcImage);
Cv2.WaitKey(1); // do events
}
}
}

Environment

Ubuntu 18.04 Desktop 64bit

What did you do when you faced the problem?

Just tried to run the program.

Output:

Unable to load shared library 'OpenCvSharpExtern' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: libOpenCvSharpExtern: cannot open shared object file: No such file or directory

Unhandled Exception: System.TypeInitializationException: The type initializer for 'OpenCvSharp.NativeMethods' threw an exception. ---> OpenCvSharp.OpenCvSharpException: Unable to load shared library 'OpenCvSharpExtern' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: libOpenCvSharpExtern: cannot open shared object file: No such file or directory ---> System.DllNotFoundException: Unable to load shared library 'OpenCvSharpExtern' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: libOpenCvSharpExtern: cannot open shared object file: No such file or directory
at OpenCvSharp.NativeMethods.core_Mat_sizeof()
at OpenCvSharp.NativeMethods.TryPInvoke() in C:\projects\opencvsharp\src\OpenCvSharp\PInvoke\NativeMethods.cs:line 136
--- End of inner exception stack trace ---
at OpenCvSharp.NativeMethods.TryPInvoke() in C:\projects\opencvsharp\src\OpenCvSharp\PInvoke\NativeMethods.cs:line 145
at OpenCvSharp.NativeMethods..cctor() in C:\projects\opencvsharp\src\OpenCvSharp\PInvoke\NativeMethods.cs:line 60
--- End of inner exception stack trace ---
at OpenCvSharp.NativeMethods.imgcodecs_imread(String filename, Int32 flags)
at OpenCvSharp.Mat..ctor(String fileName, ImreadModes flags) in C:\projects\opencvsharp\src\OpenCvSharp\Modules\core\Mat\Mat.cs:line 78
at ConsoleApp01.Program.Main(String[] args) in /home/suityou01/installation/test/ConsoleApp01/Program.cs:line 10

What did you intend to be?

To compile and run ok