Add support for .net standard 2.0

[Sicos1977]

Hi,

First a big thanks for this project.

Can you also support .net standard 2.0? In version 11 you only support .net standard 2.1 and this prevents me from installing it in a .net 4.8 application because that only supports .net standard 2.0

[tinohager]

Hi, we need some new features from .net standard 2.1 that are unfortunately not available in the previous version.

[jcasale]

Hi @tinohager ,
Is it something we can polyfill without impacting the current code?

I also have some code that must support the older framework.

[tinohager]

I would recommend setting up a web API or other communication between them and using the new version for the SMTP server.

[Sicos1977]

What is the special thing you needed that is only in .net standard 2.1?

[tinohager]

By default, sslStream.AuthenticateAsServerAsync does not provide a CancellationToken. A workaround would need to be implemented here for the error case. For the old .NET Framework. This would also mean that the tests would have to be carried out with a switch for the old framework... Which would lead to considerable additional effort overall.

https://github.com/cosullivan/SmtpServer/pull/235/files#diff-4338d83ddc3d50123ba5f345b860e140d5e0e2d13d289c8211cb6506f3d5324aR53

[Sicos1977]

Why don't you just use some #IF statements in your code? This way you have some extra work but in the end you can support the old and new.

[tinohager]

@Sicos1977 As an open-source developer, I contribute to this project without financial compensation. If someone is interested in continuing support for the legacy .NET Framework, they are very welcome to step in and take ownership of that effort. Alternatively, earlier versions of the project remain available for use. I am not the maintainer of this project, but for me, the focus lies on modern development rather than maintaining backward compatibility with outdated platforms.

[Sicos1977]

@tinohager, I know it takes som effort because I have more than one opensource project on GitHub that also supports the old .net frameworks. Sometimes your stuck on the old platforms because Microsoft like to f*ck with developers by not supporting webforms on newer frameworks. In the company where I'am working we have a huge webforms project that is 20 years old and still works very good and new things are being added. Yes you can re-develop this with razor or blazor but that takes at least a year to do and you know how it goes in big companies... they don't want to spend money on that.

That is also the reason why I'm stuck on the old .net framework, just because Microsoft stops development on something. But Google does exactly the same :-)

I'll try to look into the code this weekend and make it also work on the old .net framework with #IF statements in the code if you are open for a pull request.

[tinohager]

To be honest, I would extract the logic and build interfaces between the old project and the new one based on a WebApi or WebSockets. That would get rid of dependencies.

The pull requests have to be accepted by @cosullivan; I'm only a contributor myself. I've already made my personal opinion on the #IF statements in this project clear :)

[BobbyCannon]

@Sicos1977 As an open-source developer, I contribute to this project without financial compensation. If someone is interested in continuing support for the legacy .NET Framework, they are very welcome to step in and take ownership of that effort. Alternatively, earlier versions of the project remain available for use. I am not the maintainer of this project, but for me, the focus lies on modern development rather than maintaining backward compatibility with outdated platforms.

THIS CANNOT BE STATED CLEARLY ENOUGH!

"As an open-source developer, I contribute to this project without financial compensation."

Too many people do not understand the amount of effort it takes to maintain and contribute to open source. Most of it is in our free time as a fun thing to do. Supporting old frameworks and old dependencies is not fun and it's VERY time consuming.

Thank you, @tinohager and other contributors of this project (and others) for even making it available at continuing to work on it. Open source contributors don't get enough credit.