I'm trying to add some middleware to search and replace specific things in the html output of a page. I've made the middleware for this, but I can't figure out how to register it correctly. I've tried registering like mentioned in https://docs.umbraco.com/umbraco-cms/reference/routing/custom-middleware using the PostPipeline. But when I debug things, the middleware is hit before my controller endpoint is hit. Is there some way I can change the order?

for CSP Manager I am doing:

builder.Services.Configure<UmbracoPipelineOptions>(options =>
        {
#if NET8_0_OR_GREATER
            options.AddFilter(new UmbracoPipelineFilter(
                CspConstants.PackageAlias,
                postPipeline: applicationBuilder =>
                {
                    applicationBuilder.UseMiddleware<CspMiddleware>();
                }));
        });
#else
            options.AddFilter(new UmbracoPipelineFilter(
                CspConstants.PackageAlias,
                _ => { },
                applicationBuilder =>
                {
                    applicationBuilder.UseMiddleware<CspMiddleware>();
                },
                _ => { }));
        });
#endif

There is also an event on the HttpContext that you can hook into that gets fired right before the response is sent to the client. I'm on my phone right now, but it's something similar to :`httpContext.OnBeforeSendingHeaders`

Must have had something wrong in my middleware, reworked it a bit, and now it works 🙂

@skttl Middleware get's hit in both directions of the ASP.Net Core pipeline, to know whether your on the inbound request or the outbound response you should hook into the

context.Response

event bits I believe inside the InvokeAsync method.. something a bit like this:

cs
 context.Response.OnStarting(async () =>
        {
           //maniuplate response here - but watch out for things like content length headers ending up incorrect
}

(https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware/request-response?view=aspnetcore-8.0#startasync might help with that.)

You can use PostPipeline, or UseUmbraco().WithMiddleware(.. ADD YOUR MIDDLEWARE HERE), but also just the regular UseMiddleware methods.

This one is golden, for avoiding the

System.InvalidOperationException: The response headers cannot be modified because the response has already started.

have already been sent!