• author: Nick Chapsas

Interceptors: A Sneak Peek into the Future of C# 12

In this article, we will dive into an intriguing feature coming in C# 12 called interceptors. As an experimental addition to the language, interceptors give us a glimpse into the future of .NET and where it is headed. This feature is expected to be released for .NET 8 and C# 12, but let's not make any assumptions just yet.

Note: As this feature is in preview, developers will need to explicitly opt-in when it becomes available. By going to the Cs project and saving the features.interceptors.preview, developers can enable this experimental feature.

Introduction to Interceptors

Interceptors are a powerful tool that allows developers to capture and modify method invocations. Traditionally, achieving this level of control required using external libraries like PostSharp or emitting code at runtime. However, with C# 12's interceptors, developers will have a built-in solution.

The Intercept Location Attribute

To demonstrate the usage of interceptors, let's consider a simple .NET 8 console application. We will utilize an extension method called MyInterceptorMethod to intercept the invocation of a specific method.

By placing the InterceptLocation attribute at the specified location within the code, we can intercept the method invocation and modify its behavior. This attribute requires the absolute path of the file containing the invocation, the line number, and the character position of the method invocation.

Example Implementation

In the example below, we have a class called Example with a method called MyMethod. We want to intercept the invocations of this method and modify the output. By using the InterceptLocation attribute, we can achieve this. Let's take a closer look:

publicclassExample{publicvoidMyMethod(stringworld){Console.WriteLine($"Hello {world}");}}publicstaticclassMyInterceptorClass{[InterceptLocation("<absolute_path>/Program.cs", 5, 9)]publicstaticvoidMyInterceptorMethod(thisExampleexample,stringworld){Console.WriteLine($"Hello Brave New {world}");}}

In this code snippet, the MyInterceptorClass extension method intercepts the invocation of MyMethod from the Example class. When the intercepted method is called, the interceptor replaces it with a modified behavior.

The Magic Behind Interceptors

Interceptors utilize compile-time interception, allowing them to intercept method invocations before runtime. This feature becomes especially important in the context of ahead-of-time (AOT) compilation, as .NET is rapidly shifting towards full AOT compilation.

By intercepting methods at compile time and accessing their parameters, developers gain a granular control over their code's behavior. This compile-time interception ensures efficiency and avoids the complexities associated with runtime code emission.

Multiple Interceptions

Developers can also intercept multiple lines of code within a single method invocation. By using multiple InterceptLocation attributes or duplicating the entire interception code block, developers can intercept multiple invocations and introduce different behaviors.

Feedback and Future Possibilities

As interceptors are still in the experimental stage, it's crucial for developers to provide feedback and suggestions. This helps refine the feature and ensure its usefulness in real-world scenarios. You can find the proposal for interceptors in the description of this video, where you can also try it out and share your feedback.

Source Generators: Optimizing the Future of .NET

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In this article, we will delve into the exciting realm of Source Generators, a new feature in .NET that aims to optimize and enhance the capabilities of the framework. We will explore the purpose and potential of Source Generators while also addressing some concerns and inviting your feedback. But before we dive in, let's provide a brief overview of this groundbreaking technology.

What are Source Generators?

Source Generators are a powerful new addition to the .NET ecosystem. They allow for the automatic generation of source code during compilation, paving the way for improved performance and enhanced developer productivity. Essentially, Source Generators analyze your code and, under certain conditions, generate additional code to augment or replace existing code constructs.

Why are Source Generators being introduced?

One key driving factor behind the introduction of Source Generators is the desire to make .NET a fully Ahead-of-Time (AOT) compatible project or framework. By enabling Source Generators to write code, Microsoft aims to further optimize and enable native IoT development within the .NET ecosystem. This move is necessary as runtime called Dynamic assembly loading and various other runtime features are not compatible with AOT.

How do Source Generators work?

You may be wondering how Source Generators obtain necessary information, such as file locations, during code generation. Well, the good news is that you are not expected to manually write these code snippets. Source Generators can utilize techniques to access this information and generate the code reliably. For example, you can employ a "get Interceptor file path" method and add the microsoft.codeanalysis.com package to resolve names during compilation. Rest assured, these intricate details are well-handled by Source Generator authors, so you need not fret about writing them manually.

What are the benefits of Source Generators?

The benefits of Source Generators are vast and varied. On one hand, they empower performance improvements by allowing detection and optimization of code patterns that could be replaced with statically generated alternatives. For instance, functions like Regex.IsMatch can be replaced with statically generated matchers instead of the ones emitted at runtime. Similarly, Source Generators can optimize code related to minimal API endpoints and dependency injection, enabling the use of static compile-time safe versions rather than relying on reflection.

Invoking Your Feedback:

As Source Generators are still in the preview stage, it is crucial to provide feedback to help shape and refine this exciting new feature. I encourage you to click on the link in the article description, access the provided resources, and try out Source Generators yourself. Share your experiences, opinions, and concerns with the community. Your valuable input will aid in creating a robust and reliable Source Generator ecosystem for the future of .NET.

Potential Concerns:

While Source Generators offer immense potential, some concerns may arise. One potential worry is the possibility of abuse by certain NuGet package authors. This concern arises due to the extensive capabilities of Source Generators, which could be misused if not properly regulated. As this technology evolves, it is essential to address potential risks and ensure that appropriate safeguards are in place.Interceptors offer an exciting glimpse into c# 12's future. while still in preview, this experimental feature demonstrates microsoft's commitment to enhancing the capabilities of the .net ecosystem. by providing compile-time interception, interceptors open new doors for developers to modify and control their code effectively. stay tuned for further updates on this cutting-edge development in c# 12.


In this article, we explored the world of Source Generators in the .NET ecosystem. We learned about their purpose, functionality, and potential impact on the future of .NET development. We highlighted the importance of your feedback in shaping this feature and addressing any concerns that may arise. So, take the opportunity provided in the article description to try out Source Generators, share your thoughts, and contribute to the advancement of this exciting new frontier in .NET. Happy coding!

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