Document known differences between .NET Framework and .NET Core

[twsouthwick]

I couldn't find any specific documentation about major diferences between .NET Framework and Core, but some of the topics that should be covered:

• Replacement for AppDomain's scenario of assembly isolation
• Replacement for AppDomain's scenario of remoting

There are probably other topics, but I encountered these two recently and figuring out what should be done to replace it was difficult. Samples for it would be helpful.

[mairaw]

I think we talk about these differences on the porting docs but we don't have a top-level topic on these differences: https://docs.microsoft.com/en-us/dotnet/articles/core/porting/libraries

On this section: Key Technologies Not Yet Available on the .NET Standard or .NET Core

[svick]

There is also Porting to .NET Core on the .Net Blog, which contains a section on what you should use instead of discontinued technologies like AppDomain.

[cartermp]

Moving to backlog for now until we get more clarification on API changes.

[mairaw]

@terrajobst @weshaggard would you guys be the right people to talk about this issue?

[weshaggard]

@jkotas would probably be the best person to talk with on this subject but I don't think we really have any clear cut guidance for replacements in this space.

[jkotas]

Remoting: Doc update tracked by https://github.com/dotnet/corefx/issues/18394. The issue has some discussion about the options.

Assembly isolation: AssemblyLoadContext is the replacement. Documentation in https://github.com/dotnet/coreclr/blob/master/Documentation/design-docs/assemblyloadcontext.md. https://blogs.msdn.microsoft.com/dotnet/2016/05/27/making-it-easier-to-port-to-net-core/#comment-77765 and https://github.com/dotnet/coreclr/issues/295#issuecomment-75266259 has some more context.