Building a Custom Middleware Pipeline Logic

Snippet

Building a Custom Middleware Pipeline Logic

Framework-like architectures are often built on the Chain of Responsibility pattern. This snippet demonstrates how to manually construct a middleware pipeline using higher-order functions. Each 'Use' call wraps the next component, allowing for pre- and post-processing logic without external libraries.

snippet.cs

csharp

public delegate Task RequestDelegate(string context);
 
public class PipelineBuilder
{
    private readonly List<Func<RequestDelegate, RequestDelegate>> _components = new();
 
    public void Use(Func<RequestDelegate, RequestDelegate> middleware)
    {
        _components.Add(middleware);
    }
 
    public RequestDelegate Build()
    {
        RequestDelegate app = (context) => Task.CompletedTask;
        for (int i = _components.Count - 1; i >= 0; i--)
        {
            app = _components[i](app);
        }
        return app;
    }
}

Breakdown

public delegate Task RequestDelegate(string context)

The core abstraction representing an asynchronous operation in the pipeline.

app = _components[i](app)

Recursively wraps delegates to create a nested execution chain (functional composition).

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