Project-system: Adding a new type to a class designer file shows an error

[davkean]

1. Create a new Console App (.NET Core)
2. Right-click project -> Add -> New Item -> Class Diagram
3. Right-click on the diagram and choose Add Class

Expected: For a new file to be added
Actual:

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Microsoft Visual Studio
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The XPath query / is not supported.
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OK   
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[davkean]

The underlying cause here is that ProjectTypeGuid ("Kind") that we're returning is not recognized so CodeController.GetLanguage is throwing:

``` C#

            string kind = owner.Project.Kind;
            if (string.Compare(kind, ProjectKinds.CSharpProjectKind, StringComparison.Ordinal) == 0)
                result = CodeHandler.CMLanguageCSharp;
            else if (string.Compare(kind, ProjectKinds.VBProjectKind, StringComparison.Ordinal) == 0)
                result = CodeHandler.CMLanguageVB;
            else if (string.Compare(kind, ProjectKinds.CppProjectKind, StringComparison.Ordinal) == 0)
                result = CodeHandler.CMLanguageCPP;
            else
                throw new System.NotSupportedException(CodeHandler.CodeHandlerExceptions.CDUnknownLangNotSupported(kind));

```

[sagrapro7]

@davkean have you solved the problem with "The XPath query / is not supported." error?

[MaverickMartyn]

Bumping this for a status update as well. :)

[randyhockin]

This is very disappointing. Class Diagram support in VS 2017 for C# Core has been buggy for 6+ months. I just downloaded the latest patch version and it still does not work.

It is a great productivity feature when creating your initial models for new projects and the only practical way to visualize larger models.

Very disappointing.

[MaverickMartyn]

I guess we will have to try and do it ourselves. Unfortunately it seems that parts of the buggy code is proprietary, and thus not available for us to change.

[davkean]

Microsofties, I've an internal PR for this here: https://devdiv.visualstudio.com/DevDiv/_git/CPS/pullrequest/122409?_a=files.

[jklaus]

@davkean any chance there is an ETA the resolution? ETA to customers that is.

[davkean]

The above PR unblocks some portion of the class diagram code so that it recognizes the project system, but until we've tested it end-to-end I cannot give a timeline.

[davkean]

I've confirmed the above PR gets further, but it's sometimes running into:

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Microsoft Visual Studio
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The code for C:\Users\davkean\Source\Repos\ConsoleApp334\ConsoleApp334\Class3.cs is not ready to be read yet. In some cases, saving all files and generating again will fix this issue.
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OK   
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Which underneath is caused by: https://github.com/dotnet/project-system/issues/2544, which we are also tackling in 15.8.

[davkean]

This exact issue will be fixed in 15.8 Preview 3, however, as mentioned above there is sometimes still an issue when adding a file as mentioned above. That cause is being tracked by https://github.com/dotnet/project-system/issues/2544.