Compatibility shim used by .NET Standard 2.0

by

This works by creating all the necessary libraries that are referenced by classic .NET libraries.

E.g. in .NET Core the implementation of Object or Attribute is defined in System.Runtime. When you compile code, the generated code always references the assembly and the type => [System.Runtime]System.Object. Classic .NET projects however reference System.Object from mscorlib. When trying to use a classic .NET assembly on .NET Core 1.0/1.1, this usually leads to types not being found. In .NET Core 2.0, there will be “fake” types in a mscorlib that the runtime knows how to forward to where the implementation actually is.

You can read more about how this assembly unification works on the dotnet/standard GitHub repo but the most important scenario is this (image taken from this repository):

mscorlib facade

This shows how the scenario is supposed to work: When a 3rd party dll references [mscorlib]Microsoft.Win32.RegistryKey, there will be an mscorlib.dll that contains a type forward to [Microsoft.Win32.Registry] Microsoft.Win32.RegistryKey so it will work when a Microsoft.Win32.RegistryKey.dll is present.

This also shows the major downside: The registry is a windows-only concept and not available on Mac or Linux so this particular code may fail to run on non-windows platforms. But if you use only parts of the library that do not use this functionality, it may work for cross-platform scenarios.

Another problem is that even if API is “available” to compile against and reference, it still may throw a PlatformNotSupportedException.

For example, a library that implements a file format for serialisation / deserialisation might work without modification, even if it has been built for .NET Framework 3.5.

To find what API functions a particular library uses, the .NET Portability Analyzer can be used to scan a dll and show if the library is compatible and if not, which APIs are blocking.

More Related Contents:

  1. Build .NET Core console application to output an EXE
  2. What is the difference between .NET Core and .NET Standard Class Library project types?
  3. Is ConfigurationManager.AppSettings available in .NET Core 2.0?
  4. Should I take ILogger, ILogger, ILoggerFactory or ILoggerProvider for a library?
  5. Auto Versioning in Visual Studio 2017 (.NET Core)
  6. Compile a .NET Core application as an EXE file using Visual Studio 2017
  7. Azure Function gives error: System.Drawing is not supported on this platform
  8. .NET Standard vs .NET Core
  9. Copy all dependencies from .Net Standard libraries to .Net Framework Console application
  10. Should HttpClient instances created by HttpClientFactory be disposed?
  11. How to get “Manage User Secrets” in a .NET Core console-application?
  12. Failed to find a valid digest in the ‘integrity’ attribute for resource in Blazor app
  13. Visual studio 2017 Update 3 – The SDK ‘Microsoft.NET.Sdk.Web’ specified could not be found
  14. Use HttpClientFactory from .NET 4.6.2
  15. How to read AppSettings values from a .json file in ASP.NET Core
  16. Return file in ASP.Net Core Web API
  17. Encrypted configuration in ASP.NET Core
  18. Automatic native and managed DLLs extracting from Nuget Package
  19. Windows Forms Designer and WPF Designer for .NET Core
  20. Send HTTP POST message in ASP.NET Core using HttpClient PostAsJsonAsync
  21. Startup.cs in a self-hosted .NET Core Console Application
  22. Can WPF applications be run in Linux or Mac with .Net Core 3?
  23. Proper way to start and fire-and-forget asynchronous calls?
  24. System.Text.Json: Deserialize JSON with automatic casting
  25. Is it possible to run a .NET Core console application silently (hide console window)?
  26. Azure – Unhandled Exception: System.IO.FileNotFoundException
  27. Getting nested properties with System.Text.Json
  28. Using .net standard 1.5 lib in .net 4.6.2 misses System.Runtime 4.1.0.0
  29. Net Core: Execute All Dependency Injection in Xunit Test for AppService, Repository, etc
  30. ASP.NET Core configuration for .NET Core console application

Leave a Comment