Why should you care?

ShopNest import pipeline (parse → validate → save) should be reorderable and testable per step.

See it live — copy this example

Paste into a C# console or class library project and run dotnet run.

public delegate Task PipelineDelegate(PipelineContext ctx);
public sealed class PipelineContext { public string Payload { get; set; } = ""; }
public static class PipelineBuilder
{
    public static PipelineDelegate Build(params Func<PipelineContext, PipelineDelegate, Task>[] layers)
    {
        PipelineDelegate next = _ => Task.CompletedTask;
        for (var i = layers.Length - 1; i >= 0; i--)
        {
            var layer = layers[i];
            var current = next;
            next = ctx => layer(ctx, current);
        }
        return next;
    }
}

var run = PipelineBuilder.Build(
    async (ctx, next) => { ctx.Payload = ctx.Payload.Trim(); await next(ctx); },
    async (ctx, next) => { Console.WriteLine(ctx.Payload); await next(ctx); }
);
await run(new PipelineContext { Payload = "  HD-100  " });

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• Layers wrap next delegates — same onion as ASP.NET middleware.
• Build once; run many times.

Practice next

1. Run the trim+print pipeline.
2. Add a validate layer that throws on empty.
3. Compare to middleware mental model.
4. Add timing layer.
5. Short-circuit on invalid payload.

Remember

Composable steps. Onion next(). Same idea as middleware.

ShopNest import pipeline

Parse → validate → save as pipeline layers.

Outcome: New validation plugs in without rewriting Run().