in ASP.NET Core, is there any way to set up middleware from Program.cs?

Question

I am building a support library for ASP.NET Core websites. I have a few pieces of middleware that need to be enabled, and they need to be added before any other middleware due what they do.

I can create an extension method on IWebHostBuilder to add services, likewise for configuring logging, but I don't see any way to add middleware in a programmatic way. Is there any way to do this? Looking at the source for WebHost/WebHostBuilder nothing jumped out.

---

Given the first comment, I may not have been clear enough. I know how to create middleware and use it. What I am trying to do is ensure that when the Configure(IApplicationBuilder app) method is called on Startup by the framework, my middleware is already in place. In a similar manner to being able to do ServiceConfiguration prior to Startup even being created. So an extension method like

public static IWebHostBuilder AddPayscaleHostingServices(this IWebHostBuilder webHostBuilder, string serviceName)
{
    return webHostBuilder.ConfigureServices(collection =>
    {
        collection.RegisterPayscaleHostingServices();
    }).ConfigureLogging(factory =>
    {

    });
}

gives me the ability to do some setup prior to the webHostBuilder.Build method, but I don't see anything similar for middleware/anything on IApplicationBuilder.

Thanks, Erick

Answer 1

You could use a startup filter to achieve this. Startup filters allow you to configure middleware from a service resolved from the DI container.

Defining a startup filter is easy:

public class MyStartupFilter : IStartupFilter
{
    public Action<IApplicationBuilder> Configure(Action<IApplicationBuilder> next)
    {
        return app =>
        {
            // Configure middleware
            // ...

            // Call the next configure method
            next(app);
        };
    }
}

Always make sure to call next(app) or any other middleware won't be configured.

Now register the startup filter as a singleton implementation of IStartupFilter in your ConfigureServices method:

services.AddSingleton<IStartupFilter, MyStartupFilter>();