我最近开始学习Roslyn Code Analysis.我经历了提供的示例代码.我的问题如下：

有没有办法如何获取从引用的库加载的符号的XML文档注释？

我使用的示例代码是FAQ(7).我们的目标是获得一个Console.Write函数的文档注释.

    public void GetWriteXmlComment()
    {
        var project1Id = ProjectId.CreateNewId();
        var document1Id = DocumentId.CreateNewId(project1Id);

        var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);

        var solution = new AdhocWorkspace().CurrentSolution
            .AddProject(project1Id, "Project1", "Project1", LanguageNames.CSharp)
            .AddMetadataReference(project1Id, mscorlib);

        var declarations = SymbolFinder.FindDeclarationsAsync(solution.Projects.First(), "Write", true).Result;

        var decFirst = declarations.First();
        var commentXml = decFirst.GetDocumentationCommentXml();
    }

示例代码适用于某些方法 – 它获取文档文本.但是对于方法,例如Console.Write,它使用NullDocumentationProvider,因此返回空字符串.

UPDATE

我发现我可以使用TestDocumentationProvider实例加载MetadataReference,如下所示：

        var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location,
            default(MetadataReferenceProperties), new TestDocumentationProvider());

其中TestDocumentationProvider实现了Microsoft.CodeAnalysis DocumentationProvider抽象类.

    private class TestDocumentationProvider : DocumentationProvider
    {
        protected override string GetDocumentationForSymbol(string documentationMemberID, CultureInfo preferredCulture, CancellationToken cancellationToken = default(CancellationToken))
        {
            // To-Be-Done
        }
    }

现在问题缩小到如何使用documentationMemberID阅读文档？

解决方法:

更新：在Roslyn 2.0中,您可以使用XmlDocumentationProvider.CreateFromFile.

我能想到的唯一方法是使用Reflection创建FileBasedXmlDocumentationProvider(或以其他方式从GitHub复制其实现).您还需要搜索引用程序集,因为框架程序集的加载位置不包含文档.

private static MetadataReference FromType(Type type)
{
    var path = type.Assembly.Location;
    return MetadataReference.CreateFromFile(path, documentation: GetDocumentationProvider(path));
}

private static string GetReferenceAssembliesPath()
{
    var programFiles =
        Environment.GetFolderPath(Environment.Is64BitOperatingSystem
            ? Environment.SpecialFolder.ProgramFilesX86
            : Environment.SpecialFolder.ProgramFiles);
    var path = Path.Combine(programFiles, @"Reference Assemblies\Microsoft\Framework\.NETFramework");
    if (Directory.Exists(path))
    {
        var directories = Directory.EnumerateDirectories(path).OrderByDescending(Path.GetFileName);
        return directories.FirstOrDefault();
    }
    return null;
}

private static DocumentationProvider GetDocumentationProvider(string location)
{
    var referenceLocation = Path.ChangeExtension(location, "xml");
    if (File.Exists(referenceLocation))
    {
        return GetXmlDocumentationProvider(referenceLocation);
    }
    var referenceAssembliesPath = GetReferenceAssembliesPath();
    if (referenceAssembliesPath != null)
    {
        var fileName = Path.GetFileName(location);
        referenceLocation = Path.ChangeExtension(Path.Combine(referenceAssembliesPath, fileName), "xml");
        if (File.Exists(referenceLocation))
        {
            return GetXmlDocumentationProvider(referenceLocation);
        }
    }
    return null;
}

private static DocumentationProvider GetXmlDocumentationProvider(string location)
{
    return (DocumentationProvider)Activator.CreateInstance(Type.GetType(
        "Microsoft.CodeAnalysis.FileBasedXmlDocumentationProvider, Microsoft.CodeAnalysis.Workspaces.Desktop"),
        location);
}

我在RoslynPad中使用了类似的东西.