This package targets .NET Standard 2.0+ and .NET 5.0 or later.

Old version

RzR.Web.Middleware.ETag is ASP.NET Core middleware that adds HTTP validators to eligible responses and evaluates conditional request headers against the current response state.

It supports:

• automatic ETag generation from the response body
• request-specific ETag and Last-Modified values through delegates
• conditional request handling for If-Match, If-None-Match, and If-Modified-Since
• DI-based replacement of the ETag generator through IETagGenerator
• endpoint-level opt-in, opt-out, and route-specific overrides on .NET 5+

Supported frameworks

Endpoint metadata features such as WithETag(), WithoutETag(), and ETagOptionsAttribute are available when your application consumes the .NET 5+ build of the package.

Installation

Install-Package RzR.Web.Middleware.ETag

dotnet add package RzR.Web.Middleware.ETag

Quick start

Prefer configuring the middleware in DI with AddETag(...), then add UseETag() to the pipeline.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using RzR.Web.Middleware.ETag;

public class Startup
{
	public void ConfigureServices(IServiceCollection services)
	{
		services.AddRouting();
		services.AddETag();
	}

	public void Configure(IApplicationBuilder app)
	{
		app.UseRouting();

		app.UseETag();

		app.UseEndpoints(endpoints =>
		{
			endpoints.MapGet("/etag", async context =>
			{
				context.Response.ContentType = "text/plain";
				await context.Response.WriteAsync("payload");
			});
		});
	}
}

When you use explicit endpoint routing, place UseETag() after UseRouting() and before UseEndpoints(...) so endpoint metadata can be resolved correctly.

Common configuration

services.AddETag(options =>
{
	options.MaxBodySize = 1024 * 1024;
	options.ETagFactory = context => $"resource:{context.Request.Path}";
	options.LastModifiedFactory = _ => DateTimeOffset.UtcNow;
});

Default behavior:

• only GET requests are processed unless you extend SupportedMethods
• only 200 OK responses receive an ETag
• range requests, WebSocket requests, server-sent events, and oversized buffered bodies are skipped
• a matching If-None-Match on GET or HEAD produces 304 Not Modified
• a failing If-Match, or a matching If-None-Match on an unsafe method, produces 412 Precondition Failed

Documentation

1. USING
2. CHANGELOG
3. MIGRATION