Learn Source Generator in .NET

Overview

Ever wanted to type less for the most common things you type over and over? Oh yes, me too. Probably would shave off 6-months lost time over the years.

Geting started

Basic Generator

1. Create 2 projects:
   • Console App: Sample.ConsoleApp
   • Standard Library: Learn.SourceGenerator
2. Add NuGet packages to the Standard Lib project, Microsoft.CodeAnalysis.Analyzers and Microsoft.CodeAnalysis.CSharp.

Console App

1. In the console app, change the class type from internal class to partial class.
2. Next, add our method we're going to generate

namespace Sample.ConsoleApp;

// Refactor fron `internal class` to `partial class`
partial class Program
{
  static partial void HelloFrom(string name);

  static void Main(string[] args)
  {
    HelloFrom("my generated method Code");
  }
}

3. Reference the source generator library
4. Modify the Console App's csproj file

<!-- Add this as a new ItemGroup, replacing paths and names appropriately -->
<ItemGroup>
    <ProjectReference Include="..\PathTo\SourceGenerator.csproj"
                      OutputItemType="Analyzer"
                      ReferenceOutputAssembly="false" />
</ItemGroup>

Generator - Standard Library

using Microsoft.CodeAnalysis;

namespace Learn.SourceGenerator
{
  [Generator]
  public class HelloGenerator : ISourceGenerator
  {
    public void Execute(GeneratorExecutionContext context)
    {
      // Code generation goes here

      // Find the main method
      var mainMethod = context.Compilation.GetEntryPoint(context.CancellationToken);

      // Build up the source code
      string source = $@" // Auto-generated code
using System;

namespace {mainMethod.ContainingNamespace.ToDisplayString()}
{{
  public static partial class {mainMethod.ContainingType.Name}
  {{
    static partial void HelloFrom(string name) =>
      Console.WriteLine($""Generator says: Hi from '{{name}}'"");
  }}
}}
";
      var typeName = mainMethod.ContainingType.Name;

      // Add the source code to the compilation
      context.AddSource($"{typeName}.g.cs", source);
    }

    public void Initialize(GeneratorInitializationContext context)
    {
      // No initialization required for this one
    }
  }
}

References

• Source Generator Overview
  • Source Generators Cookbook
• Community Toolkit
  • Sample Property Generator
• Collection of Source Generators
• Blog - Source Generators
• 4 Ways To Generate Code