The new API does not work on .NET Framework < 4.7.1

[yaeldekel]

It relies on the extension method in System.Linq "Append" that was added only in 4.7.1.

[eerhardt]

Unfortunately there are a few methods in .NET Standard 2.0 which aren't available in .NET Framework 4.6.1, but 4.6.1 "claims" it supports .NET Standard 2.0.

Here is the list: https://github.com/dotnet/standard/blob/205332796a9a0f869ff698402c3496f14cc71f50/netstandard/src/ApiCompatBaseline.net461.txt

/cc @ericstj @terrajobst @weshaggard

[markusweimer]

Does this mean we'd have to raise the min version of .NET Framework required for ML.NET 0.6?

[eerhardt]

Does this mean we'd have to raise the min version of .NET Framework required for ML.NET 0.6?

If we don't fix this issue for 0.6, Yes. If someone tries running the new API on an older .NET Framework, they will an exception.

[markusweimer]

@TomFinley how strong is our dependency on the method mentioned by Yael? Can we code around this? Maybe for 0.7?

[Zruty0]

umm, I think we could just add our implementation of Append to TLC until we upgrade the .NET version?

Append(x) is the same as Concat(new[] {x})

[markusweimer]

umm, I think we could just add our implementation of Append to TLC until we upgrade the .NET version?

Sounds good. Can we make it conditional on the version of .NET a user has?

[Zruty0]

Also, I'm not too strongly attached to Append. I only used it because my C# was rusty, and I forgot that 'there is no Append in LINQ'. And sure enough, it appeared while I was not looking, just not in the old framework.

[markusweimer]

@Zruty0, is this fixable between now and 0.6?

[yaeldekel]

I can create a PR today.

[yaeldekel]

I looked at the list that @eerhardt posted, and Append looks like the only API that we use in there.

[markusweimer]

Cool! Unless you have a bug to fix for 0.6, it would be great to get this done before the release.