SourceGenerator 已经出来很久了，也一直在关注。之前观摩大佬 xljiulang 的 WebApiClient 使用 SourceGenerator 生成接口代理类，深受启发，准备拿过来用看看（发出白嫖的声音），写个编译期静态代理AOP。本篇重点是怎么获取元数据，得到想要的数据，生成想要的代码（往下拖到第 4 点）。
几个月前写了个demo，现在趁着有空重新整理完善了下。.net 6 新增了个 IIncrementalGenerator 进行增量编译，这个还没研究，后面再说。
我的思路是继承，生成一个类去继承需要拦截的实际类，然后重写相关的方法，此时插入额外的方法，比如 Before，After 等。这就要求相关方法必须是 可重写 的， virtual 或 override。好了，开干。
1、定义Aop属性，打个标签，SourceGenerator 根据这个标签查找相关的 class 或 interface
1 /// <summary>
2 /// Aop 拦截器
3 /// </summary>
4 public interface IAopInterceptor
5 {
6 /// <summary>
7 /// 执行前操作，同步方法调用
8 /// </summary>
9 /// <param name="context"></param>
10 /// <returns></returns>
11 AopContext Before(AopContext context);
12 /// <summary>
13 /// 执行前操作，异步方法调用
14 /// </summary>
15 /// <param name="context"></param>
16 /// <returns></returns>
17 ValueTask<AopContext> BeforeAsync(AopContext context);
18 /// <summary>
19 /// 执行后操作，同步方法调用
20 /// </summary>
21 /// <param name="context"></param>
22 /// <returns></returns>
23 AopContext After(AopContext context);
24 /// <summary>
25 /// 执行后操作，异步方法调用
26 /// </summary>
27 /// <param name="context"></param>
28 /// <returns></returns>
29 ValueTask<AopContext> AfterAsync(AopContext context);
30 /// <summary>
31 /// 执行方法，同步方法调用
32 /// </summary>
33 /// <param name="context"></param>
34 /// <returns></returns>
35 AopContext Next(AopContext context);
36 /// <summary>
37 /// 执行方法，异步方法调用
38 /// </summary>
39 /// <param name="context"></param>
40 /// <returns></returns>
41 ValueTask<AopContext> NextAsync(AopContext context);
42 }
可以不要 IAopInterceptor 这个接口，这里加了只是为了约束。
1 public class AopInterceptor : Attribute, IAopInterceptor
2 {
3 /// <summary>
4 /// 是否执行 Before
5 /// </summary>
6 public bool HasBefore { get; set; }
7 /// <summary>
8 /// 是否执行 After
9 /// </summary>
10 public bool HasAfter { get; set; }
11 /// <summary>
12 /// 是否执行 Aop 的 Next
13 /// </summary>
14 public bool HasAopNext { get; set; }
15 /// <summary>
16 /// 是否执行实际的方法
17 /// </summary>
18 public bool HasActualNext { get; set; }
19
20 /// <summary>
21 /// 默认执行所以方法
22 /// </summary>
23 public AopInterceptor()
24 {
25 HasBefore = true;
26 HasAopNext = true;
27 HasActualNext = true;
28 HasAfter = true;
29 }
30
31 public virtual AopContext Before(AopContext context) => context;
32
33 public virtual async ValueTask<AopContext> BeforeAsync(AopContext context)
34 {
35 await ValueTask.CompletedTask;
36 return context;
37 }
38
39 public virtual AopContext After(AopContext context)
40 {
41 return context.Exception != null ? throw context.Exception : context;
42 }
43
44 public virtual async ValueTask<AopContext> AfterAsync(AopContext context)
45 {
46 if (context.Exception != null)
47 throw context.Exception;
48
49 await ValueTask.CompletedTask;
50 return context;
51 }
52
53 public virtual AopContext Next(AopContext context)
54 {
55 try
56 {
57 context.Invoke();
58 }
59 catch (Exception e)
60 {
61 context.Exception = e;
62 }
63 return context;
64 }
65
66 public virtual async ValueTask<AopContext> NextAsync(AopContext context)
67 {
68 try
69 {
70 context = await context.InvokeAsync();
71 }
72 catch (Exception e)
73 {
74 context.Exception = e;
75 }
76
77 return context;
78 }
79 }
2、定义上下文，主要包含 是否是异步，是否有返回值，还有实际方法的委托。决定了调用实际方法的时候怎么调用
1 /// <summary>
2 /// Aop 上下文
3 /// </summary>
4 public struct AopContext
5 {
6 /// <summary>
7 /// 是否是异步
8 /// </summary>
9 public bool IsTask { get; private set; }
10 /// <summary>
11 /// 是否有返回值
12 /// </summary>
13 public bool HasReturnValue { get; private set; }
14 /// <summary>
15 /// 方法输入参数
16 /// </summary>
17 public Dictionary<string, dynamic> MethodInputParam { get; private set; }
18
19 /// <summary>
20 /// 实际方法执行结果，可能是 Task
21 /// </summary>
22 public Func<dynamic> ActualMethod { get; set; }
23 /// <summary>
24 /// 返回值，具体的值
25 /// </summary>
26 public dynamic ReturnValue { get; set; }
27 /// <summary>
28 /// 异常信息
29 /// </summary>
30 public Exception Exception { get; set; }
31 /// <summary>
32 /// IServiceProvider
33 /// </summary>
34 public IServiceProvider ServiceProvider { get; private set; }
35
36 /// <summary>
37 /// 初始化
38 /// </summary>
39 /// <param name="serviceProvider"></param>
40 /// <param name="methodInputParam"></param>
41 /// <param name="isTask"></param>
42 /// <param name="hasReturnValue"></param>
43 /// <param name="actualMethod"></param>
44 public AopContext(IServiceProvider serviceProvider, Dictionary<string, dynamic> methodInputParam, bool isTask, bool hasReturnValue, Func<dynamic> actualMethod) : this()
45 {
46 ServiceProvider = serviceProvider;
47 MethodInputParam = methodInputParam;
48 IsTask = isTask;
49 HasReturnValue = hasReturnValue;
50 ActualMethod = actualMethod;
51 }
52
53 /// <summary>
54 /// 执行实际方法 异步
55 /// </summary>
56 /// <returns></returns>
57 public async ValueTask<AopContext> InvokeAsync()
58 {
59 if (ActualMethod == null)
60 return this;
61
62 if (HasReturnValue)
63 {
64 ReturnValue = await ActualMethod();
65 return this;
66 }
67
68 await ActualMethod();
69 return this;
70 }
71
72 /// <summary>
73 /// 执行实际方法 同步
74 /// </summary>
75 /// <returns></returns>
76 public void Invoke()
77 {
78 if (ActualMethod == null)
79 return;
80
81 //特殊处理 同步且没有返回值，用 Task.Run 包装
82 if (!IsTask && !HasReturnValue)
83 ActualMethod.Invoke().GetAwaiter().GetResult();
84 else
85 ReturnValue = ActualMethod.Invoke();
86 }
87 }
3、硬编码实现类
3.1、定义拦截器
1 /// <summary>
2 /// 常规服务，执行所有方法
3 /// </summary>
4 public class SampleAttribute : AopInterceptor
5 {
6 /// <summary>执行前操作，同步方法调用</summary>
7 /// <param name="context"></param>
8 /// <returns></returns>
9 public override AopContext Before(AopContext context)
10 {
11 Console.WriteLine("Before...");
12 return base.Before(context);
13 }
14
15 /// <summary>执行前操作，异步方法调用</summary>
16 /// <param name="context"></param>
17 /// <returns></returns>
18 public override ValueTask<AopContext> BeforeAsync(AopContext context)
19 {
20 Console.WriteLine("BeforeAsync...");
21 return base.BeforeAsync(context);
22 }
23
24 public override AopContext After(AopContext context)
25 {
26 Console.WriteLine("After...");
27 return context;
28 }
29
30 /// <summary>执行后操作，异步方法调用</summary>
31 /// <param name="context"></param>
32 /// <returns></returns>
33 public override ValueTask<AopContext> AfterAsync(AopContext context)
34 {
35 Console.WriteLine("AfterAsync...");
36 return base.AfterAsync(context);
37 }
38
39 /// <summary>执行方法，同步方法调用</summary>
40 /// <param name="context"></param>
41 /// <returns></returns>
42 public override AopContext Next(AopContext context)
43 {
44 Console.WriteLine("Next...");
45 return base.Next(context);
46 }
47
48 /// <summary>执行方法，异步方法调用</summary>
49 /// <param name="context"></param>
50 /// <returns></returns>
51 public override ValueTask<AopContext> NextAsync(AopContext context)
52 {
53 Console.WriteLine("NextAsync...");
54 return base.NextAsync(context);
55 }
56 }
定义接口
1 public interface ITestService
2 {
3 [Sample]
4 DateTime SampleSync();
5
6 [Sample]
7 ValueTask<DateTime> SampleAsync();
8 }
3.2、定义实现类
1 public class TestService : ITestService
2 {
3
4 public virtual DateTime SampleSync()
5 {
6 return DateTime.Now;
7 }
8
9 public virtual async ValueTask<DateTime> SampleAsync()
10 {
11 await ValueTask.CompletedTask;
12 return DateTime.Now;
13 }
14 }
3.3、定义继承类，重写相关方法
1 public sealed class TestService_Aop : TestService
2 {
3 private readonly IServiceProvider _serviceProvider0;
4 public TestService_Aop(IServiceProvider serviceProvider0)
5 {
6 _serviceProvider0 = serviceProvider0;
7 }
8
9 public override DateTime SampleSync()
10 {
11 var aopContext = new AopContext(_serviceProvider0,
12 new Dictionary<string, dynamic>() { },
13 false,
14 true,
15 null);
16
17 var aopInterceptor0 = _serviceProvider0.GetRequiredService<SampleAttribute>();
18 if (aopInterceptor0.HasBefore) aopContext = aopInterceptor0.Before(aopContext);
19 if (aopInterceptor0.HasAopNext)
20 {
21 if (aopInterceptor0.HasActualNext)
22 {
23 aopContext.ActualMethod = () => base.SampleSync();
24 }
25 aopContext = aopInterceptor0.Next(aopContext);
26 }
27 else
28 {
29 if (aopInterceptor0.HasActualNext)
30 {
31 aopContext.ReturnValue = base.SampleSync();
32 }
33 }
34 if (aopInterceptor0.HasAfter) aopContext = aopInterceptor0.After(aopContext);
35
36 return aopContext.ReturnValue;
37 }
38
39 public override async ValueTask<DateTime> SampleAsync()
40 {
41 var aopContext = new AopContext(_serviceProvider0,
42 new Dictionary<string, dynamic>() { },
43 true,
44 true,
45 null);
46
47 var aopInterceptor0 = _serviceProvider0.GetRequiredService<SampleAttribute>();
48 if (aopInterceptor0.HasBefore) aopContext = await aopInterceptor0.BeforeAsync(aopContext);
49 if (aopInterceptor0.HasAopNext)
50 {
51 if (aopInterceptor0.HasActualNext)
52 {
53 aopContext.ActualMethod = () => base.SampleAsync();
54 }
55 aopContext = await aopInterceptor0.NextAsync(aopContext);
56 }
57 else
58 {
59 if (aopInterceptor0.HasActualNext)
60 {
61 aopContext.ReturnValue = await base.SampleAsync();
62 }
63 }
64 if (aopInterceptor0.HasAfter) aopContext = await aopInterceptor0.AfterAsync(aopContext);
65
66 return aopContext.ReturnValue;
67 }
68 }
4、开整
4.1、新建项目 Mic.Aop.Generator，TargetFramework 选 netstandard2.0，引入两个分析器包
<ItemGroup>
<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.3.1" PrivateAssets="all" />
<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.3">
<PrivateAssets>all</PrivateAssets>
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
</ItemGroup>
4.2、新建类 AopGenerator，继承 ISourceGenerator 接口，实现 Execute 方法，Execute 的内容是最终的成品。
1 /// <summary>
2 /// 代码生成器
3 /// </summary>
4 [Generator]
5 public class AopGenerator : ISourceGenerator
6 {
7 /// <summary>
8 /// 初始化
9 /// </summary>
10 /// <param name="context"></param>
11 public void Initialize(GeneratorInitializationContext context)
12 {
13 //Debugger.Launch();
14
15 context.RegisterForSyntaxNotifications(() => new AopSyntaxReceiver());
16 }
17
18 /// <summary>
19 /// 执行
20 /// </summary>
21 /// <param name="context"></param>
22 public void Execute(GeneratorExecutionContext context)
23 {
24 if (context.SyntaxReceiver is AopSyntaxReceiver receiver)
25 {
26 var aopMateData = receiver
27 .FindAopInterceptor() // 查找所有的拦截器
28 .GetAopMetaData(context.Compilation); //根据拦截器找到所有的类或方法，获取元数据，包含所有接口、实现类、所有属性、所有方法
29
30 var builders = aopMateData
31 .GetAopCodeBuilderMetaData() //获取用于构建代码的元数据，过滤出需要的数据
32 .Select(i => new AopCodeBuilder(i))
33 .Distinct()
34 .ToList();
35 //开始生成代码
36 foreach (var builder in builders)
37 {
38 context.AddSource(builder.SourceCodeName, builder.ToSourceText());
39 }
40 }
41 }
42 }
4.3、AopSyntaxReceiver 语法树处理类，这一步获取到所有的数据：接口、类、属性、方法、参数等等等
/// <summary>
/// 语法接收器
/// </summary>
sealed class AopSyntaxReceiver : ISyntaxReceiver
{
private const string GeneratorTagName = "AopInterceptor"; //所有拦截器需要继承的基类
private const string IgnoreAttribute = "IgnoreAopAttribute"; //忽略aop
/// <summary>
/// 类列表
/// </summary>
private readonly List<ClassDeclarationSyntax> _classSyntaxList = new List<ClassDeclarationSyntax>();
/// <summary>
/// 接口列表
/// </summary>
private readonly List<InterfaceDeclarationSyntax> _interfaceSyntaxList = new List<InterfaceDeclarationSyntax>();
/// <summary>
/// 所有的AopInterceptor
/// </summary>
public List<string> AopAttributeList = new List<string>();
/// <summary>
/// 所有的AopInterceptor
/// </summary>
public List<ClassMetaData> AopAttributeClassMetaDataList = new List<ClassMetaData>(); /// <summary>
/// 访问语法树
/// </summary>
/// <param name="syntaxNode"></param>
void ISyntaxReceiver.OnVisitSyntaxNode(SyntaxNode syntaxNode)
{
if (syntaxNode is InterfaceDeclarationSyntax interfaceSyntax)
{
this._interfaceSyntaxList.Add(interfaceSyntax);
} if (syntaxNode is ClassDeclarationSyntax classSyntax)
{
this._classSyntaxList.Add(classSyntax);
}
} //其他代码........
}
4.4、找到所有的拦截器
1 /// <summary>
2 /// 找出所有 AopInterceptor
3 /// </summary>
4 /// <returns></returns>
5 public AopSyntaxReceiver FindAopInterceptor()
6 {
7 foreach (var classSyntax in this._classSyntaxList)
8 {
9 var root = classSyntax.SyntaxTree.GetRoot();
10 var classesWithAttribute = root
11 .DescendantNodes()
12 .OfType<ClassDeclarationSyntax>()
13 .ToList();
14
15 if (!classesWithAttribute.Any())
16 continue;
17
18 foreach (var classDeclarationSyntax in classesWithAttribute)
19 {
20 if (classDeclarationSyntax.BaseList == null)
21 continue;
22
23 foreach (BaseTypeSyntax baseTypeSyntax in classDeclarationSyntax.BaseList.Types)
24 {
25 if (baseTypeSyntax.ToString().Trim() == GeneratorTagName)
26 {
27 AopAttributeList.Add(classDeclarationSyntax.Identifier.Text);
28
29 var meta = GetClassMetaData(classSyntax);
30 if (meta != null && AopAttributeClassMetaDataList.All(d => d.Name != meta.Name))
31 AopAttributeClassMetaDataList.Add(meta);
32 }
33 }
34 }
35 }
36
37 AopAttributeList = AopAttributeList.Distinct().ToList();
38
39 return this;
40 }
4.5、找到所有接口和打了标记的class
1 /// <summary>
2 /// 获取所有打了标记的接口和类
3 /// </summary>
4 /// <param name="compilation"></param>
5 /// <returns></returns>
6 public AopMetaData GetAopMetaData(Compilation compilation)
7 {
8 var result = new AopMetaData(AopAttributeList, IgnoreAttribute, new List<InterfaceMetaData>(), new List<ClassMetaData>());
9
10 if (!AopAttributeList.Any())
11 return result;
12
13 //处理接口
14 foreach (var classSyntax in this._interfaceSyntaxList)
15 {
16 var root = classSyntax.SyntaxTree.GetRoot();
17 var interfaceWithAttribute = root
18 .DescendantNodes()
19 .OfType<InterfaceDeclarationSyntax>()
20 .ToList();
21
22 if (!interfaceWithAttribute.Any())
23 continue;
24
25 //处理接口
26 foreach (var interfaceDeclaration in interfaceWithAttribute)
27 {
28 var namespaceName = interfaceDeclaration.FindParent<NamespaceDeclarationSyntax>().Name.ToString();
29 var className = interfaceDeclaration.Identifier.Text;
30 var properties = interfaceDeclaration.DescendantNodes().OfType<PropertyDeclarationSyntax>().ToList();
31 var methodSyntaxs = interfaceDeclaration.DescendantNodes().OfType<MethodDeclarationSyntax>().ToList();
32
33 //属性集合
34 var props = properties.Select(d => new PropertyMetaData(d.Identifier.Text, d.GetAttributeMetaData())).ToList();
35 //方法集合
36 var methods = methodSyntaxs.Select(GetMethodMetaData).ToList();
37
38 var interfaceMetaData = new InterfaceMetaData(namespaceName, className, interfaceDeclaration.GetAttributeMetaData(), props, methods);
39 if (interfaceMetaData.MethodMetaData.Any() && !result.InterfaceMetaDataList.Exists(d => d.Equals(interfaceMetaData)))
40 result.InterfaceMetaDataList.Add(interfaceMetaData);
41 }
42 }
43
44 //处理类
45 foreach (var classSyntax in this._classSyntaxList)
46 {
47 var root = classSyntax.SyntaxTree.GetRoot();
48 var classesWithAttribute = root
49 .DescendantNodes()
50 .OfType<ClassDeclarationSyntax>()
51 .ToList();
52
53 if (!classesWithAttribute.Any())
54 continue;
55
56 foreach (var classDeclaration in classesWithAttribute)
57 {
58 var classMetaData = GetClassMetaData(classDeclaration);
59 if (classMetaData == null)
60 continue;
61
62 if (AopAttributeList.Contains(classMetaData.Name))
63 continue;
64
65 if (classMetaData.MethodMetaData.Any() && !result.ClassMetaDataList.Exists(d => d.Equals(classMetaData)))
66 result.ClassMetaDataList.Add(classMetaData);
67 }
68 }
69
70 result.AopAttributeClassMetaDataList = AopAttributeClassMetaDataList;
71
72 return result;
73 }
4.6、获取 class 的信息：属性、方法集合、继承的接口、using引用、构造函数
1 private ClassMetaData? GetClassMetaData(ClassDeclarationSyntax classDeclaration)
2 {
3 var namespaceName = classDeclaration.FindParent<NamespaceDeclarationSyntax>().Name.ToString();
4 var className = classDeclaration.Identifier.Text;
5 var properties = classDeclaration.DescendantNodes().OfType<PropertyDeclarationSyntax>().ToList();
6 var methodSyntaxs = classDeclaration.DescendantNodes().OfType<MethodDeclarationSyntax>().ToList();
7
8 //属性集合
9 var props = properties.Select(d => new PropertyMetaData(d.Identifier.Text, d.GetAttributeMetaData())).ToList();
10 //方法集合
11 var methods = methodSyntaxs.Select(GetMethodMetaData).ToList();
12 //实现的接口集合
13 var interfaces = classDeclaration.BaseList?.ToString().Split(':').Last().Trim().Split(',').Where(d => d.Split('.').Last().StartsWith("I")).ToList() ?? new List<string>();
14 //using 引用
15 var usingDirectiveSyntax = classDeclaration.Parent?.Parent == null ? new SyntaxList<UsingDirectiveSyntax>() : ((CompilationUnitSyntax)classDeclaration.Parent.Parent).Usings;
16 var usings = usingDirectiveSyntax.Select(d => d.ToString()).ToList();
17
18 //构造函数
19 var constructorDictionary = new List<KeyValueModel>();
20 foreach (var memberDeclarationSyntax in classDeclaration.Members)
21 {
22 if (memberDeclarationSyntax.Kind().ToString() == "ConstructorDeclaration")
23 {
24 //constructorDictionary = memberDeclarationSyntax.DescendantNodes().OfType<ParameterSyntax>().ToDictionary(d => d.GetFirstToken().Text, d => d.GetLastToken().Text);
25 constructorDictionary = memberDeclarationSyntax.DescendantNodes().OfType<ParameterSyntax>().Select(d => new KeyValueModel(d.Type?.ToString(), d.Identifier.Text)).ToList();
26 break;
27 }
28 }
29
30 return new ClassMetaData(namespaceName, className, classDeclaration.GetAttributeMetaData(), props, methods, interfaces, constructorDictionary, usings);
31 }
4.7、获取 method 的信息：方法名称、是否异步、是否有返回值、是否可重写、参数信息、Aop 标记集合（可能有多个）
1 private MethodMetaData GetMethodMetaData(MethodDeclarationSyntax methodDeclarationSyntax)
2 {
3 var param = new List<KeyValueModel>();
4 var properties = methodDeclarationSyntax.DescendantNodes().OfType<ParameterListSyntax>().FirstOrDefault()?.DescendantNodes().OfType<ParameterSyntax>().ToList() ?? new List<ParameterSyntax>();
5 foreach (var parameterSyntax in properties)
6 {
7 var type = parameterSyntax?.Type?.ToString();
8 var name = parameterSyntax?.Identifier.Text;
9 if (type != null && name != null)
10 param.Add(new KeyValueModel(type, name));
11 }
12
13 var returnValue = methodDeclarationSyntax.ReturnType.ToString();
14
15 return new MethodMetaData(methodDeclarationSyntax.Identifier.Text,
16 methodDeclarationSyntax.GetAttributeMetaData(), returnValue, param, methodDeclarationSyntax.Modifiers.ToString());
17 }
4.8、一顿操作猛如虎，现在我们获取到了所有的信息，可以开干了。这一步处理元数据，过滤出需要生成代理类的信息。
约定一些规则：
就近原则：类方法上的标签 > 类上的标签 > 接口方法上的标签 > 接口上的标签，即离实际的方法越近，优先级越高。
忽略Aop：打上 [IgnoreAop] 标签
管道模式：如果一个方法打上多个Attribute，则按照管道的原则，先进后出，注意，只有最接近方法的 Attribute 才能调用 Next 方法。如果有 三个 Attribute，分别是 attribute1、attribute2、attribute3，则执行顺序是 attribute1.Before => attribute2.Before => attribute3.Before => attribute3.Next => attribute3.After => attribute2.After => attribute1.After
按照这个约定，过滤得到需要的数据
public List<AopCodeBuilderMetaData> GetAopCodeBuilderMetaData()
{
//就近原则，方法 > 类 > 接口方法 > 接口 var list = new List<AopCodeBuilderMetaData>();
foreach (var classMetaData in ClassMetaDataList.Where(d => !AopAttributeList.Contains(d.Name)))
{
////必须要可重写方法 放出错误
//if (classMetaData.MethodMetaData.All(d => !d.CanOverride))
// continue; var methods = new List<MethodMetaData>();
var classHasIgnore = classMetaData.HasIgnore(IgnoreAttribute); //实现的接口
classMetaData.Usings.Add(classMetaData.NameSpace);
classMetaData.InterfaceMetaData = InterfaceMetaDataList.Where(d => classMetaData.Interfaces.Contains(d.Key)
|| classMetaData.Interfaces.SelectMany(t => classMetaData.Usings.Select(u => $"{u.Replace("using ", "").Replace(";", "")}.{t.Split('.').Last()}")).Contains(d.Key)).ToList();
classMetaData.Usings.Remove(classMetaData.NameSpace); //按照就近原则过滤
//foreach (var methodMetaData in classMetaData.MethodMetaData.Where(d => d.CanOverride))
foreach (var methodMetaData in classMetaData.MethodMetaData)
{
//忽略
if (methodMetaData.AttributeMetaData.HasIgnore(IgnoreAttribute))
continue; //类方法标记
var methodAttrs = methodMetaData.AttributeMetaData.GetAopAttributes(AopAttributeList);
if (methodAttrs.Any())
{
methodMetaData.AttributeMetaData.Clear();
methodMetaData.AttributeMetaData.AddRange(methodAttrs);
methods.Add(methodMetaData);
continue;
} //类标记
if (classHasIgnore)
continue; var classAttr = classMetaData.AttributeMetaData.GetAopAttribute(AopAttributeList);
if (classAttr != null)
{
methodMetaData.AttributeMetaData.Clear();
methodMetaData.AttributeMetaData.Add(classAttr);
methods.Add(methodMetaData);
continue;
} //接口标记
if (!classMetaData.Interfaces.Any())
continue; //接口方法忽略
if (classMetaData.InterfaceMetaData.Any(d => d.MethodMetaData.FirstOrDefault(m => m.Key == methodMetaData.Key)?.AttributeMetaData.HasIgnore(IgnoreAttribute) == true))
continue; //接口方法标记
var interfaceMethodAttr = classMetaData.InterfaceMetaData.Select(d => d.MethodMetaData.FirstOrDefault(m => m.Key == methodMetaData.Key)?.AttributeMetaData.GetAopAttribute(AopAttributeList))
.FirstOrDefault(d => d != null); if (interfaceMethodAttr != null)
{
methodMetaData.AttributeMetaData.Clear();
methodMetaData.AttributeMetaData.Add(interfaceMethodAttr);
methods.Add(methodMetaData);
continue;
} //接口标记
var interfaceAttr = classMetaData.InterfaceMetaData.Where(d => d.MethodMetaData.Any(d => d.Key == methodMetaData.Key)).Select(d => d.AttributeMetaData.GetAopAttribute(AopAttributeList))
.FirstOrDefault(d => d != null);
if (interfaceAttr != null)
{
methodMetaData.AttributeMetaData.Clear();
methodMetaData.AttributeMetaData.Add(interfaceAttr);
methods.Add(methodMetaData);
continue;
}
} if (methods.Any())
list.Add(new AopCodeBuilderMetaData(classMetaData.NameSpace, classMetaData.Name, methods, classMetaData.Constructor, classMetaData.Usings, classMetaData.InterfaceMetaData));
} return list;
}
4.9、生成代码，生成 3.3 这样的代码。这一步就是代码拼接，StringBuilder 一把梭，需要注意的是处理不同的情况如 同步异步、有无返回值、方法的重载、拦截器的传值等。代码太原始不宜展示，感兴趣的可以去看源码。整个过程到此结束。
5、不服跑个分（bushi）
加上aop标签之后，整个方法调用链是 aopbefore => aopnext => 执行实际的方法 => aopafter，一共4层，每多一层，耗时就增加，在我的电脑上跑了一下，每增加一层调用，大概增加 20~30ns 的耗时。因此根据实际使用场景，增加了 HasBefore、HasAfter、HasAopNext、HasActualNext 这4个判断去自定义需要执行的方法。详情见1。
缓存场景：有缓存，直接 before 里获取缓存，直接返回，不需要后续的执行，此时只有before；无缓存：可以在 AopNext 中执行 ActualNext，更新缓存然后返回，或者 执行 ActualNext ，最后在 After 中更新缓存，这里可以省略一个方法调用；
业务日志：只需要执行 ActualNext，然后在 After 中写日志，这场景只有2个方法，节省2个方法，美滋滋。
以直接调用同步方法为基准，36ns
直接调用同步方法：1
直接调用异步方法：2.08
缓存场景同步调用：5.47
缓存场景异步调用：7.45
4个方法火力全开：同步：3.8
4个方法火力全开：异步：13.5
代码中使用了.net core 自带的DI 获取对象，有 几十ns 的开销。
6、结尾
SourceGenerator是个好东西，我司在用的场景还有生成一些额外属性，比如 给Dto中的 枚举、字典、行政区划等自动添加 Name 属性，不用手动一个个去处理，延长键盘使用寿命。
在这里提供了一些思路，你们用来做什么呢？
本文代码传送门：https://github.com/ad313/mic
另外分享一些SourceGenerator的项目：
https://github.com/amis92/csharp-source-generators
https://github.com/Cysharp/MemoryPack