C# 源生成器使用方法

搭建项目环境

1. 创建 Net Standard 2.0 项目

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<Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <TargetFramework>netstandard2.0</TargetFramework> <LangVersion>latest</LangVersion> <IsRoslynComponent>true</IsRoslynComponent>  <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules> </PropertyGroup> <ItemGroup> <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.9.2" /> <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" /> </ItemGroup> </Project>

2. 生成器完整结构示例

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// 示例功能：自动将自定义类型的属性的内部属性展开为可直接访问的属性 [Generator] // 生成器特性标记，同时继承 IIncrementalGenerator internal class FlattenPropsGenerator : IIncrementalGenerator { // 需要实现的方法，完成代码生成 public override void Initialize(IncrementalGeneratorInitializationContext context) { // 创建语法提供者，查找带有 GenerateFlattenAttribute 的属性进行处理 var propertyPipeline = context.SyntaxProvider .CreateSyntaxProvider( predicate: (node, _) => QuickCheckAttribute(node), // 快速筛选语义节点 transform: (context, _) => TransformClass(context)) // 转换为特定对象便于后续操作 .Where(classInfo => classInfo != null); // 注册生成代码输出 context.RegisterSourceOutput(propertyPipeline, (spc, source) => { if (source is ClassFlattenInfo classFlattenInfo) GenerateFlattenedProperties(spc, classFlattenInfo); }); } /*-------------- 以下代码为具体业务实现 --------------*/ // 仅处理特定特性标注的类及属性 private static readonly string flattenPropsAttrFullName = typeof(GenerateFlattenPropsAttribute).FullName; private static readonly string flattenAttrFullName = typeof(GenerateFlattenAttribute).FullName; // 快速校验当前节点是否需要处理 private static bool QuickCheckAttribute(SyntaxNode node) { // 检查是否为 record if (node is not RecordDeclarationSyntax typeDeclaration) return false; // 检查是否包含特性 return typeDeclaration.AttributeLists.SelectMany(a => a.Attributes).Any(a => flattenPropsAttrFullName.Contains(a.Name.ToFullString())); } private static ClassFlattenInfo? TransformClass(GeneratorSyntaxContext context) { var typeDeclaration = (TypeDeclarationSyntax)context.Node; var semanticModel = context.SemanticModel; var compilation = semanticModel.Compilation; // 获取 Compilation // 获取类型符号 if (semanticModel.GetDeclaredSymbol(typeDeclaration) is not INamedTypeSymbol symbol) return null; // 检查是否有指定的特性 var flattenPropsAttributeType = compilation.GetTypeByMetadataName(flattenPropsAttrFullName); var attribute = symbol.GetAttributes().FirstOrDefault(attr => SymbolEqualityComparer.Default.Equals(attr.AttributeClass, flattenPropsAttributeType)); if (attribute == null) return null; // 查找所有带有特性的属性 var properties = new List<PropertyTransformResult>(); var attributeType = compilation.GetTypeByMetadataName(flattenAttrFullName); foreach (var property in typeDeclaration.Members.OfType<PropertyDeclarationSyntax>()) { // 获取属性符号 var propertySymbol = semanticModel.GetDeclaredSymbol(property); if (propertySymbol == null) continue; // 获取属性类型 if (propertySymbol.Type is not INamedTypeSymbol propertyType) continue; // 检查是否有特性 var attr = propertySymbol.GetAttributes().FirstOrDefault(attr => SymbolEqualityComparer.Default.Equals(attr.AttributeClass, attributeType)); if (attr == null) continue; var attrConfig = AttrConfig.CreateFromAttr(attr, context.SemanticModel); // 获取需要展平的属性 properties.Add(new PropertyTransformResult { PropertySymbol = propertySymbol, PropertyType = propertyType, PropertyName = property.Identifier.Text, PropertySyntax = property, PropertiesToFlatten = propertyType.GetAllProperties() }); } return properties.Count == 0 ? null : new ClassFlattenInfo { ContainingType = symbol, Properties = properties, IsRecord = symbol.IsRecord }; } // 根据配置信息生成对应的代码 private static void GenerateFlattenedProperties(SourceProductionContext context, ClassFlattenInfo classFlattenInfo) { var classInfo = classFlattenInfo.ContainingType; try { // 生成扁平化属性代码 var code = GenerateFlattenPropertiesCode(classFlattenInfo, context); // 添加源文件 var fileName = $"{classInfo.Name}_FlattenProps.g.cs"; context.AddSource(fileName, SourceText.From(code, Encoding.UTF8)); } catch (Exception ex) { // 报告诊断信息 var descriptor = new DiagnosticDescriptor("FLATTEN001", "Error generating flattened properties", "Error: {0}", "Generation", DiagnosticSeverity.Error, true); var diagnostic = Diagnostic.Create(descriptor, classInfo.DeclaringSyntaxReferences.First().GetSyntax().GetLocation(), ex.Message); context.ReportDiagnostic(diagnostic); } } // 生成扁平化属性代码 private static string GenerateFlattenPropertiesCode(ClassFlattenInfo classFlattenInfo, SourceProductionContext context) { var sb = new StringBuilder(); var clsInfo = classFlattenInfo.ContainingType; AddGenerateInfo(sb); // 收集所有需要 using 的命名空间 AddUsings(sb, classFlattenInfo); // 添加命名空间 var namespaceName = clsInfo.ContainingNamespace.ToDisplayString(); if (!string.IsNullOrEmpty(namespaceName)) sb.AppendLine($"namespace {namespaceName};"); // 添加类型声明 AddTypeDeclaration(sb, clsInfo); // 添加扁平化属性 AddFlattenedProperties(sb, classFlattenInfo, context); sb.AppendLine("}"); // 结束类型声明 return sb.ToString(); } private static void AddUsings(StringBuilder sb, ClassFlattenInfo classFlattenInfo) { // 收集所有需要 using 的命名空间 var usings = new HashSet<string>(); var clsNsp = classFlattenInfo.ContainingType.ContainingNamespace; Stack<ITypeSymbol> stack = new(classFlattenInfo.Properties.Select(p => p.PropertySymbol.Type) .Concat(classFlattenInfo.Properties.SelectMany(prop => prop.PropertiesToFlatten .SelectMany(x => x.GetAttributes().Select(a => a.AttributeClass))).OfType<ITypeSymbol>())); while (stack.Count > 0) { var _tsym = stack.Pop(); // 1. 添加属性类型的命名空间 if (_tsym.ContainingNamespace is { } ns && !SymbolEqualityComparer.Default.Equals(ns, clsNsp)) usings.Add(ns.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)); // 2. 添加属性类型中泛型参数的命名空间 if (_tsym is INamedTypeSymbol namedType && namedType.IsGenericType) foreach (var typeArg in namedType.TypeArguments) stack.Push(typeArg); } foreach (var s in usings) sb.AppendLine($"using {s};"); sb.AppendLine(); } private static void AddTypeDeclaration(StringBuilder sb, INamedTypeSymbol clsInfo) { sb.AppendLine($"{clsInfo.DeclaredAccessibility.ToCodeString()} {clsInfo.GetTypeModifiers()} partial {clsInfo.GetTypeKindString()} {clsInfo.Name}"); sb.AppendLine("{"); } private static void AddFlattenedProperties(StringBuilder sb, ClassFlattenInfo classFlattenInfo, SourceProductionContext context) { // 收集所有需要扁平化的属性，避免重复 var flattenedProperties = new Dictionary<string, (IPropertySymbol, PropertyTransformResult)>(); var conflicts = new List<(string msg, PropertyTransformResult prop)>(); // 现有类的属性 var existingProperty = new HashSet<string>(classFlattenInfo.ContainingType.GetMembers().OfType<IPropertySymbol>().Select(x => x.Name)); foreach (var propertyInfo in classFlattenInfo.Properties) { foreach (var prop in propertyInfo.PropertiesToFlatten) { var propertyName = prop.Name; var msg = flattenedProperties.ContainsKey(propertyName) ? $"{propertyInfo.PropertyName}.{propertyName}" : ""; if (msg == "" && existingProperty.Contains(propertyName)) msg = $"{propertyInfo.PropertyName}.{propertyName} (已存在于类中)"; if (msg != "") { conflicts.Add((msg, propertyInfo)); continue; } flattenedProperties[propertyName] = (prop, propertyInfo); } } // 报告冲突 if (conflicts.Count > 0) { const string descId = "FLATTEN002"; const string msgFmt = "检测到属性名称冲突: {0}"; foreach (var (msg, prop) in conflicts) { var _msg = string.Format(msgFmt, msg); // 控制生成文件提示 sb.AppendLine($"{indent}// {DiagnosticSeverity.Warning} {descId}: {_msg}"); // 报告诊断信息 var desc = new DiagnosticDescriptor(descId, "扁平化属性冲突", _msg, "CodeGeneration", DiagnosticSeverity.Error, true); context.ReportDiagnostic(Diagnostic.Create(desc, prop.PropertySyntax.GetLocation())); } sb.AppendLine(); } // 生成属性代码 foreach (var (prop, propertyInfo) in flattenedProperties.Values) { GenerateFlattenedPropertyCode(sb, prop, propertyInfo.PropertyName); sb.AppendLine(); } } private static void GenerateFlattenedPropertyCode(StringBuilder sb, IPropertySymbol sourceProperty, string sourcePropertyName) { var propertyName = sourceProperty.Name; var propertyType = sourceProperty.Type.ToDisplayString(SymbolDisplayFormat.MinimallyQualifiedFormat); var accessibility = sourceProperty.DeclaredAccessibility.ToCodeString(); // 添加 XML 注释 sb.AppendLine($"{indent}/// <summary>"); sb.AppendLine($"{indent}/// 从 {sourcePropertyName}.{propertyName} 扁平化的属性"); sb.AppendLine($"{indent}/// </summary>"); // 生成属性 var hasGetter = sourceProperty.GetMethod != null; var hasSetter = sourceProperty.SetMethod != null && !sourceProperty.SetMethod.IsInitOnly; // 处理 required 修饰符 var isRequired = sourceProperty.IsRequired ? "required " : ""; if (hasGetter && hasSetter) { // 获取访问器的可访问性 var getterAccess = sourceProperty.GetMethod!.DeclaredAccessibility.ToCodeString(); var setterAccess = sourceProperty.SetMethod!.DeclaredAccessibility.ToCodeString(); var getterMod = getterAccess != accessibility ? $"{getterAccess} " : ""; var setterMod = setterAccess != accessibility ? $"{setterAccess} " : ""; sb.AppendLine($"{indent}{accessibility} {isRequired}{propertyType} {propertyName}"); sb.AppendLine($"{indent}{``{"); sb.AppendLine($"{indent}{indent}{getterMod}get => {sourcePropertyName}.{propertyName};"); sb.AppendLine($"{indent}{indent}{setterMod}set => {sourcePropertyName}.{propertyName} = value;"); sb.Append($"{indent}}}"); } else if (hasGetter) { sb.AppendLine($"{indent}{accessibility} {isRequired}{propertyType} {propertyName} => {sourcePropertyName}.{propertyName};"); } else if (hasSetter) { var setterAccess = sourceProperty.SetMethod!.DeclaredAccessibility.ToCodeString(); var setterMod = setterAccess != accessibility ? $"{setterAccess} " : ""; sb.AppendLine($"{indent}{accessibility} {isRequired}{propertyType} {propertyName}"); sb.AppendLine($"{indent}{``{"); sb.AppendLine($"{indent}{indent}{setterMod}set => {sourcePropertyName}.{propertyName} = value;"); sb.Append($"{indent}}}"); } } /// <summary> /// 属性转换结果 /// </summary> struct PropertyTransformResult { public IPropertySymbol PropertySymbol { get; set; } public INamedTypeSymbol PropertyType { get; set; } public string PropertyName { get; set; } public PropertyDeclarationSyntax PropertySyntax { get; set; } // 获取源类型的所有公共实例属性（非索引器） public IReadOnlyList<IPropertySymbol> PropertiesToFlatten { get; set; } } struct ClassFlattenInfo { public INamedTypeSymbol ContainingType { get; set; } public List<PropertyTransformResult> Properties { get; set; } public bool IsRecord { get; set; } } } [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)] public sealed class GenerateFlattenAttribute : Attribute{}

3. 使用示例

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public record Person { public string? Name { get; set; } } [GenerateFlattenProps] public partial record Student { [GenerateFlatten] Person Person { get; set; } = new Person(); }

如何利用 nuget 方便使用

生成器项目无法直接被其他项目作为依赖项目引用，需要借助 nuget
修改项目配置文件使生成器项目为 nuget 项目
每次修改生成器项目后重新生成，然后在测试项目中重新安装或更新 nuget

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<PropertyGroup Condition="'$(Configuration)' == 'Debug'"> <VersionSuffix>alpha</VersionSuffix> </PropertyGroup>  <PropertyGroup Condition="'$(Configuration)' == 'Preview'"> <VersionSuffix>beta</VersionSuffix> </PropertyGroup>  <PropertyGroup Condition="'$(Configuration)' == 'Release'"> <VersionSuffix></VersionSuffix> </PropertyGroup> <PropertyGroup> <IncludeBuildOutput>false</IncludeBuildOutput> <IsAnalyzer>true</IsAnalyzer> <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>  <GeneratePackageOnBuild>true</GeneratePackageOnBuild> <PackageOutputPath>$(SolutionDir)local-packages</PackageOutputPath> <PackageId>Arch.CodeGenerator</PackageId> <Version>1.2.3</Version> <Version Condition="'$(VersionSuffix)' != ''">$(Version)-$(VersionSuffix)</Version> <PackageVersion>$(Version)</PackageVersion> <Authors>会写代码的建筑师</Authors> <Description>一个源码生成器</Description>  <IncludeBuildOutput>false</IncludeBuildOutput>  <PackageType>Dependency</PackageType> <NoPackageAnalysis>true</NoPackageAnalysis> <IncludeSourceGeneratorInPackage>true</IncludeSourceGeneratorInPackage>  <IncludeSymbols>true</IncludeSymbols> <SymbolPackageFormat>snupkg</SymbolPackageFormat>  <IncludeSource>true</IncludeSource> <PublishRepositoryUrl>true</PublishRepositoryUrl> <EmbedUntrackedSources>true</EmbedUntrackedSources> </PropertyGroup>

如何让生成器项目同时作为 dll 项目

其他引用项目可与生成器共享本项目中定义的类
使用生成器的项目可直接从 nuget 安装即可使用本项目定义的类型
比如 GenerateFlattenAttribute 可直接定义在当前项目，便于统一管理

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<Target Name="CopyForPackage" BeforeTargets="GenerateNuspec"> <Copy SourceFiles="$(OutputPath)$(AssemblyName).dll" DestinationFiles="$(OutputPath)analyzers/$(AssemblyName).dll" SkipUnchangedFiles="true" /> </Target> <ItemGroup> <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.6.0" />  <None Include="$(OutputPath)$(AssemblyName).dll" Pack="true" PackagePath="lib/netstandard2.0" />  <None Include="$(OutputPath)analyzers/$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" /> </ItemGroup>

可能遇到的问题：

首次引入源生成器项目时报错，需要重启 vs 并重新生成解决方案；