在 C# 源代码生成中获取属性属性值 - IIncrementalGenerator-解网

问：

我有以下属性：

[AttributeUsage(AttributeTargets.Class)]
public class EventApplyAttribute : Attribute
{
    public string Aggregate { get; }

    public EventApplyAttribute(string aggregate)
    {
        Aggregate = aggregate;
    }
}

我像这样使用属性：

[EventApplyAttribute(nameof(BaseClass))]
public class Test : BaseEvent{}

我使用这个源生成器：

[Generator]
public class SourceGeneration : IIncrementalGenerator
{
    private const string EventApplyAttribute = "DomainLibrary.EventApplyAttribute";

    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        IncrementalValuesProvider<ClassDeclarationSyntax> classDeclarations = context.SyntaxProvider
            .ForAttributeWithMetadataName(
                EventApplyAttribute,
                predicate: (node, _) => node is ClassDeclarationSyntax,
                transform: (ctx, ct) => GetSemanticTargetForGeneration(ctx, ct))
            .Where(static m => m is not null);

        IncrementalValueProvider<(Compilation, ImmutableArray<ClassDeclarationSyntax>)> compilationAndClasses
        = context.CompilationProvider.Combine(classDeclarations.Collect());

        context.RegisterSourceOutput(compilationAndClasses,
            static (spc, source) => Execute(source.Item1, source.Item2, spc));

    }

    private static void Execute(Compilation compilation, ImmutableArray<ClassDeclarationSyntax> classes, SourceProductionContext context)
    {
    }

    private static ClassDeclarationSyntax? GetSemanticTargetForGeneration(GeneratorAttributeSyntaxContext context, CancellationToken ct)
    {
        string fullName = context.Attributes.First().AttributeClass.ToDisplayString();

        if (fullName == EventApplyAttribute)
        {
            if (context.TargetNode is not ClassDeclarationSyntax classDeclaration)
                return null;

            return classDeclaration;
        }

        return null;
    }
}

Execute 方法中的 classes 数组具有预期的类。如果我遍历数组，我会得到很多信息。有没有办法同时访问属性属性值。在这种情况下，它会是“BaseClass”吗？我什么都找不到...

C# c夏普源生成器

private static (ClassDeclarationSyntax, AttributeData) GetSemanticTargetForGeneration(GeneratorAttributeSyntaxContext context, CancellationToken ct)
{
    if (!(context.TargetNode is ClassDeclarationSyntax classDeclaration))
        return (null, null);

    AttributeData attribute = context.Attributes
        .FirstOrDefault(a => a.AttributeClass.Name == "EventApplyAttribute");

    return (classDeclaration, attribute);
}

现在，我们将返回类声明和属性数据对。您可以在方法中处理它;我不知道你的目标是什么，所以在这里我只是生成一个文件，其中包含一个带有您正在寻找的类名的注释，以表明它有效：Execute

private static void Execute(Compilation compilation, ImmutableArray<(ClassDeclarationSyntax, AttributeData)> classes, SourceProductionContext context)
{
    foreach (var (x, i) in classes.Select((x, i) => (x, i)))
    {
        TypedConstant aggregateParam = x.Item2.ConstructorArguments[0];
        
        if (aggregateParam.Kind == TypedConstantKind.Primitive &&
            aggregateParam.Value is string value)
        {
            context.AddSource(
                $"generated_{i}.g.cs",
                $"// <auto-generated/> using System; // Found param value '{value}'");
        }
    }
}

为了完整起见，您需要更改 main 方法：Initialize

public void Initialize(IncrementalGeneratorInitializationContext context)
{
    IncrementalValuesProvider<(ClassDeclarationSyntax, AttributeData)> classDeclarations = context.SyntaxProvider
        .ForAttributeWithMetadataName(
            EventApplyAttribute,
            predicate: static (node, _) => node is ClassDeclarationSyntax,
            transform: static (ctx, ct) => GetSemanticTargetForGeneration(ctx, ct))
        .Where(m => m.Item1 is not null && m.Item2 is not null);

    IncrementalValueProvider<(Compilation, ImmutableArray<(ClassDeclarationSyntax, AttributeData)>)> compilationAndClasses
    = context.CompilationProvider.Combine(classDeclarations.Collect());

    context.RegisterSourceOutput(compilationAndClasses,
        static (spc, source) => Execute(source.Item1, source.Item2, spc));
}

在 C# 源代码生成中获取属性属性值 - IIncrementalGenerator

Get attribute property value in C# source generation - IIncrementalGenerator

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