Using Source Generators in C# projects improves performance, reduces reflections, and optimizes the development experience by generating code during compilation. Specific methods include: 1. Create a class library project and reference the necessary NuGet package; 2. Implement the ISourceGenerator interface and override the Initialize and Execute methods; 3. Check the class with a specific Attribute in Execute and generate code. Common uses include attribute notification, serialization support, dependency injection registration, and constant generation. Debugging skills include outputting logs, attaching compilation processes, and writing unit test verification generation code. Be careful to avoid complex logic affecting the construction speed and select appropriate technologies such as reflection or IL Weaving based on the scene.

Using Source Generators in C# projects to generate code can improve performance, reduce the use of runtime reflections, and make the code cleaner. Compared with traditional code generation methods (such as T4 templates or runtime dynamic generation), Source Generators are executed during the compile period, will not affect the operation efficiency, and can integrate better with the IDE.

How to get started with Source Generators

To create a Source Generator, you first need to create a .NET Standard or .NET Core class library project and reference the two NuGet packages, Microsoft.CodeAnalysis.CSharp and Microsoft.CodeAnalysis.Analyzers .

Then, you need to implement the ISourceGenerator interface and override the Initialize and Execute methods in it. The former is used to register some listening actions, while the latter is where the code is actually generated.

For example: You can check whether the class in the program has a custom Attribute in the Execute method, and then generate the corresponding auxiliary class based on this information.

 [Generator]
public class MySourceGenerator: ISourceGenerator
{
    public void Initialize(GeneratorInitializationContext context)
    {
        // Register syntax receiver context.RegisterForSyntaxNotifications(() => new SyntaxReceiver());
    }

    public void Execute(GeneratorExecutionContext context)
    {
        if (context.SyntaxContextReceiver is not SyntaxReceiver receiver)
            return;

        foreach (var candidateClass in receiver.CandidateClasses)
        {
            var className = candidateClass.Identifier.Text;
            var source = $@"namespace GeneratedCode {{
    public partial class {className} {{
        public void GeneratedMethod() {{
            System.Console.WriteLine(""Hello from generated code!"");
        }}
    }}
}}";
            context.AddSource($"{className}.g.cs", source);
        }
    }
}

Common uses and applicable scenarios

Source Generators can be used to do many things, and here are some common uses:

• Property notification : For example, the implementation of INotifyPropertyChanged is automatically generated in MVVM mode.
• Serialization support : Automatically generate serialization/deserialization code for certain types to avoid runtime reflection.
• Dependency injection registration : Scan the class of a specific tag and automatically generates the registration code.
• Constant generation : Read data from external files and generate strongly typed constant classes at compile time.

All of these usages can significantly reduce runtime overhead while keeping the development experience friendly.

If you are maintaining an SDK or framework, Source Generators is a very good choice, which allows you to provide "looks automatic" functionality, and is actually done during the compilation phase.

Debugging and testing skills

Debugging Source Generators is a bit challenging because it runs during compilation. Here are some practical tips:

• Use Console.WriteLine() to output the log to the output window (see in Visual Studio).
• Create a test project, reference your Source Generator and observe the generated code.
• Attach to the compilation process (usually VBCSCompiler.exe ) for debugging in Visual Studio.
• Use Roslyn's test SDK to write unit tests to verify that the generated code is in line with expectations.

Also, be careful not to do too much complex logic in Source Generator. Because it is part of the compilation, if it is too slow, it will affect the build speed.

Some last things to note

Although Source Generators are powerful, they are not omnipotent. Some situations are more suitable for handling with runtime reflection or AOP tools. For example:

• Reflection may be easier if you are not sensitive to performance.
• If you want to modify the existing code structure instead of generating new code, it may be more suitable to use the IL Weaving tool.
• Pay attention to version compatibility. Different versions of the .NET SDK support for Source Generators is slightly different.

Basically that's it. After mastering Source Generators, you will find that many things that were previously handled by runtime can now be handled in the compilation stage. Not only does it perform well, but it is also easier to maintain.

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