.NET中的C#源生成器(Source Generators)是什么？如何编写一个来减少模板代码？

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
    <LangVersion>latest</LangVersion>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" PrivateAssets="all" />
    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
  </ItemGroup>
</Project>

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Text;
using System.Collections.Generic;
using System.Linq;
using System.Text;

[Generator]
public class NotifyPropertyChangedGenerator : ISourceGenerator
{
    public void Initialize(GeneratorInitializationContext context) { }

    public void Execute(GeneratorExecutionContext context)
    {
        // 查找标记了特定属性的类
        var classes = context.Compilation.SyntaxTrees
            .SelectMany(tree => tree.GetRoot().DescendantNodes())
            .OfType<ClassDeclarationSyntax>()
            .Where(m => m.AttributeLists.SelectMany(a => a.Attributes)
                .Any(attr => attr.Name.ToString() == "NotifyPropertyChanged"));

        foreach (var cls in classes)
        {
            var namespaceName = GetNamespace(cls);
            var className = cls.Identifier.Text;
            var source = GenerateNotifyClass(namespaceName, className);
            context.AddSource($"{className}.g.cs", SourceText.From(source, Encoding.UTF8));
        }
    }

    private static string GetNamespace(ClassDeclarationSyntax classDecl)
    {
        SyntaxNode potentialNamespaceParent = classDecl.Parent;
        while (potentialNamespaceParent != null &&
               potentialNamespaceParent is not NamespaceDeclarationSyntax)
        {
            potentialNamespaceParent = potentialNamespaceParent.Parent;
        }

        return potentialNamespaceParent is NamespaceDeclarationSyntax ns ? ns.Name.ToString() : "Generated";
    }

    private static string GenerateNotifyClass(string ns, string className)
    {
        return $@"
namespace {ns}
{{
    partial class {className} : System.ComponentModel.INotifyPropertyChanged
    {{
        public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = null)
        {{
            PropertyChanged?.Invoke(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }}

        // 示例：你可以进一步生成属性包装器
    }}
}}";
    }
}

[NotifyPropertyChanged]
public partial class Person
{
    // 源生成器会自动让此类实现 INotifyPropertyChanged
    // 你可以在子类或手动部分类中调用 OnPropertyChanged
}