An initial (not great) example for asynchronous pipeline code. See blog post for more info: https://blog.jermdavis.dev/posts/2021/pipelines-and-async BUT you probably want this gist instead, because it's the (hopefully better) v2: https://gist.github.com/jermdavis/49ecd692a16b10899eb2ee2b50770499

AsyncPipelineExample-v1.cs

async Task Main()
{
	var pipeline = new ExampleAsyncPipeline();
	var uri = new Uri("https://news.bbc.co.uk/");

	var tempFile = await pipeline.ProcessAsync(uri);

	Console.WriteLine($"{uri} saved to {tempFile}");
}

public interface IAsyncPipelineStep<TIn, TOut>
{
	Task<TOut> ProcessAsync(Task<TIn> Input);
}

public abstract class AsyncPipeline<TIn, TOut> : IAsyncPipelineStep<TIn, TOut>
{
	public Func<Task<TIn>, Task<TOut>> _pipelineSteps { get; protected set; }

	public Task<TOut> ProcessAsync(Task<TIn> Input)
	{
		return _pipelineSteps(Input);
	}

	public Task<TOut> ProcessAsync(TIn Input)
	{
		var inputTask = Task.FromResult(Input);
		return _pipelineSteps(inputTask);
	}
}

public static class AsyncPipelineStepExtensions
{
	public static Task<TOut> Step<TIn, TOut>(this Task<TIn> Input, IAsyncPipelineStep<TIn, TOut> Step)
	{
		return Step.ProcessAsync(Input);
	}
}

public class HttpFetchAsyncStep : IAsyncPipelineStep<Uri, string>
{
	private static readonly HttpClient _client = new HttpClient();
	
	public async Task<string> ProcessAsync(Task<Uri> Input)
	{
		var uri = await Input;
		return await _client.GetStringAsync(uri);
	}
}

public class DiskWriteAsyncStep : IAsyncPipelineStep<string, string>
{
	public async Task<string> ProcessAsync(Task<string> Input)
	{
		var data = await Input;
		var fileName = System.IO.Path.GetTempFileName();
		
		await System.IO.File.WriteAllTextAsync(fileName, data);
		
		return fileName;
	}
}

public class ExampleAsyncPipeline : AsyncPipeline<Uri, string>
{
	public ExampleAsyncPipeline()
	{
		_pipelineSteps = input => input
			.Step(new HttpFetchAsyncStep())
			.Step(new DiskWriteAsyncStep());
		
	}
}

Thank you Jeremy. I found your Gists through your blog posts about pipelines. I'll haven't finished reading all of them, but they are really interesting and helpful. I am using this async pipeline code as a starting point. Also, I wanted to share a ThenOptionally extension method that I wrote. (I renamed Step to Then because I think it reads better)

        public async static Task<TOutput> ThenOptionally<TInput, TOutput>(this Task<TInput> input, Func<Task<TInput>, Task<bool>> shouldProcessStep, IAsyncPipelineStep<TInput, TOutput> step) where TInput : TOutput
        {
            if (await shouldProcessStep(input))
            {
                return await step.ProcessAsync(input);
            }
            else
            {
                return await input;
            }
        }

Thanks - glad its of help.