How deeply does ASP.NET Core in Action, 3e cover Use?

Explains lambda parameters, continuation control, short-circuiting, response timing, and class-based alternatives.

Use

As explained in ASP.NET Core in Action, 3e

Use is an ASP.NET Core extension method that adds inline middleware to an application's request-processing pipeline.

Use is an ASP.NET Core extension method for adding general-purpose inline middleware to the request-processing pipeline. It can inspect or modify requests, generate responses, or pass requests to later middleware. section 31.1.3

The middleware lambda receives the current HttpContext and a Func<Task> representing the remaining pipeline. Calling next() continues processing; omitting it short-circuits the request. section 31.1.3

Respond to a health check

app.Use(async (HttpContext context, Func<Task> next) => { if (context.Request.Path.StartsWithSegments("/ping")) { context.Response.ContentType = "text/plain"; await context.Response.WriteAsync("pong"); } else { await next(); } }); Requests beginning with /ping receive pong immediately; other requests continue to the next middleware.

Use middleware can run code before and after the rest of the pipeline. Register response changes such as headers with Response.OnStarting, because later middleware may begin streaming the response after next() returns.

Inline Use calls are convenient for small components, but reusable middleware is usually better expressed as a class with a RequestDelegate constructor and public Invoke(HttpContext) method. This shape also supports dependency injection in Invoke. section 31.1.4 section 31.4

How ASP.NET Core in Action, 3e covers it

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Related concepts

middlewareuses · Middleware is an intermediate software component or layer that processes or mediates requests, messages, or operations between other components, often adding behavior or controlling their flow.
Runimplemented by · Run is an ASP.NET Core API operation that either terminates a request pipeline with middleware or starts the application host to process requests.
Func<T>uses · Func is a .NET generic delegate family representing methods with specified parameter types and a return type.
lambdauses · A lambda is a language construct that defines an unnamed function or callable, often as a value.

This explainer was generated by Manning's knowledge graph from the text of ASP.NET Core in Action, 3e. The section links point to the parts of the book it draws on.