Awareness emails: last.

Author: gfraiteur

metalama-awareness-campaign/05_last.md

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+Hi,
+
+This is the final email in our series introducing you to Metalama.
+
+Today, let's look into more advanced patterns in C# and explore how you can automate them using Metalama.
+
+## INotifyPropertyChanged
+
+If you're building a desktop or mobile app, or even a web app with client-side Blazor, you're likely familiar with the `INotifyPropertyChanged` interface. While it seems simple to implement, it can become cumbersome and error-prone as you add more complex properties and dependencies between objects.
+
+Enter the `[Observable]` aspect from the open-source [Metalama.Patterns.Observability](https://doc.postsharp.net/metalama/patterns/observability?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly) package.
+
+```csharp
+[Observable]
+public class Person
+```
+
+This aspect handles `INotifyPropertyChanged` implementation for you, supporting a rich set of scenarios:
+
+- **Automatic properties:**
+
+    ```csharp
+    public string? FirstName { get; set; }
+    ```
+
+- **Properties depending on other properties or fields:**
+
+    ```csharp
+    public string FullName => $"{this.FirstName} {this._lastName}";
+    ```
+
+- **Properties depending on child objects, such as `Person`:**
+
+    ```csharp
+    public string FullName => $"{this.Person.FirstName} {this.Person.LastName}";
+    ```
+
+- **Properties depending on properties of the base type.**
+
+Consider how much boilerplate code you'd need to properly implement `INotifyPropertyChanged` for these scenarios and how much you would save with Metalama! To see the work Metalama does for you, [check out the diff](https://doc.postsharp.net/metalama/patterns/observability/standard-cases?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly).
+
+It's not just about saving code, but also about enhancing code quality. Remember the last bug when you forgot to add a call to `OnPropertyChanged` for a computed property? With `[Observable]`, since dependency discovery is fully automatic, this won't happen any more.
+
+Read more details about `[Observable]` in our [documentation](https://doc.postsharp.net/metalama/patterns/observability?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly).
+
+## Builder Pattern
+
+Another frequent source of boilerplate code is the [Builder pattern](https://blog.postsharp.net/builder-pattern-with-metalama?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly), which has become ubiquitous in modern C# due to the increased use of immutable types.
+
+Consider a simple immutable class:
+
+```csharp
+public partial class Song
+{
+    public string Title { get; }
+
+    public ImmutableArray<string> Artists { get; }
+}
+```
+
+The code supporting the Builder class would look like this:
+
+```csharp
+public partial class Song
+{
+    private Song(string title, ImmutableArray<string> artists)
+    {
+        this.Title = title;
+        this.Artists = artists;
+    }
+
+    public Builder ToBuilder() => new Builder(this);
+
+    public class Builder
+    {
+        public string Title { get; set; }
+
+        public ImmutableArray<string>.Builder Artists { get; }
+
+        public Builder()
+        {
+            this.Artists = ImmutableArray.CreateBuilder<string>();
+        }
+
+        public Builder(Song song)
+        {
+            this.Title = song.Title;
+            this.Artists = song.Artists.ToBuilder();
+        }
+
+        public Song Build() => new Song(this.Title, this.Artists.ToImmutable());
+    }
+}
+```
+
+How repetitive! Do you really want to write this code by hand? Thankfully, [this can be automated using Metalama](https://doc.postsharp.net/metalama/examples/builder?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly), and you can tailor the code generation pattern to fit your needs.
+
+## Other Examples
+
+We can't cover all use cases of Metalama in a single email, so before wrapping up this sequence, here's a list of Metalama use cases:
+
+- [Parameter validation](https://doc.postsharp.net/metalama/examples/validation?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly) and [code contracts](https://doc.postsharp.net/metalama/patterns/contracts);
+- [Logging](https://doc.postsharp.net/metalama/examples/log?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly);
+- [Exception handling](https://doc.postsharp.net/metalama/examples/exception-handling?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly) with or without [Polly](https://doc.postsharp.net/metalama/examples/exception-handling/retry/retry-5);
+- [Caching](https://doc.postsharp.net/metalama/patterns/caching?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly) and [memoization](https://doc.postsharp.net/metalama/patterns/memoization?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly);
+- [INotifyPropertyChanged](https://doc.postsharp.net/metalama/patterns/observability), WPF [commands](https://doc.postsharp.net/metalama/patterns/wpf/command?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly), and [dependency properties](https://doc.postsharp.net/metalama/patterns/wpf/dependency-property?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly);
+- [Architecture verification](https://doc.postsharp.net/metalama/conceptual/architecture?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly);
+- [Change tracking](https://doc.postsharp.net/metalama/examples/change-tracking?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly) and the [Memento pattern](https://doc.postsharp.net/metalama/examples/memento?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly).
+- [Cloning](https://doc.postsharp.net/metalama/examples/clone?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly);
+- [Builder](https://doc.postsharp.net/metalama/examples/builde?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly), and [Singleton](https://doc.postsharp.net/metalama/examples/singleton?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly) patterns;
+- [ToString](https://doc.postsharp.net/metalama/examples/tostring) generation.
+
+For more use cases and open-source aspect implementations, visit the [Metalama Marketplace](https://www.postsharp.net/metalama/marketplace?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly).
+
+## How to Get Started?
+
+Start using Metalama today. Add the `Metalama.Framework` package to your project and activate _Metalama Free_, our free edition that lets you use up to three aspect types (e.g., logging, caching, and `INotifyPropertyChanged`) regardless of your project's size.
+
+For a better development experience, download the optional [Visual Studio Tools for Metalama](https://www.postsharp.net/metalama/download?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly).
+
+If you have any questions, feel free to reach out to our community on [GitHub](https://github.com/orgs/postsharp/discussions) or on our [Slack workspace](https://www.postsharp.net/slack?mtm_campaign=awareness&mtm_kwd=email5&mtm_source=instantly).
+
+Happy meta-programming with Metalama!