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

Defines paths, handlers, route values, and GET semantics, but does not descend into middleware implementation.

MapGet

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

MapGet is an ASP.NET Core endpoint-mapping method for associating a URL pattern and handler with HTTP GET requests.

MapGet associates a URL path with a handler for HTTP GET requests. In a minimal API, the handler generates the response when a matching request arrives; GET should retrieve data without changing server state. section 3.6 section 5.2.2

Return a greeting from the root path

WebApplicationBuilder builder = WebApplication.CreateBuilder(args); WebApplication app = builder.Build(); app.MapGet("/", () => "Hello World!"); app.Run(); This endpoint returns plain text for GET requests to /. The server begins listening only after app.Run(). section 3.6

A MapGet call has two essential parts:

The first argument is the URL path, such as / or /person/{name}. section 3.6
The second argument is a delegate that produces the response, optionally using values captured from the route. section 3.6
Use MapPost or another Map* method when the operation creates, changes, or deletes data. section 5.2.2

Table 5.1 The minimal API map endpoints and the corresponding HTML verbs (view table figure)

Method	HTTP verb	Expected operation
`MapGet(path,` `handler)`	`GET`	Fetch data only; no modification of state. May be safe to cache.
`MapPost(path,` `handler)`	`POST`	Create a new resource.
`MapPut(path,` `handler)`	`PUT`	Create or replace an existing resource.
`MapDelete(path,` `handler)`	`DELETE`	Delete the given resource.
`MapPatch(path,` `handler)`	`PATCH`	Modify the given resource.
`MapMethods(path,` `methods,` `handler)`	Multiple verbs	Multiple operations.
`Map(path,` `handler)`	All verbs	Multiple operations.
`MapFallback(handler)`	All verbs	Useful for SPA fallback routes.

Compare MapGet with the other minimal API mapping methods and their expected HTTP operations. section 5.2.2

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

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Also explained in

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.NET in Action, Second EditionMapGet is an ASP.NET Core endpoint-mapping method that associates HTTP GET requests with a handler.
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Building Web APIs with ASP.NET CoreMapGet is an ASP.NET Core minimal-API method that maps HTTP GET requests to route handlers.

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Related concepts

HTTP GETuses · HTTP GET is a request method for retrieving a representation of a resource identified by the request target, without requesting a state change.
routinguses · Routing is the selection of a path, destination, or processing component to direct an item, request, or flow toward an intended endpoint.
Problem Detailsproduces · Problem Details is a standardized HTTP response format for communicating machine-readable information about a problem occurrence, commonly serialized as JSON.
IEndpointRouteBuilderuses · IEndpointRouteBuilder is an ASP.NET Core interface for registering route endpoints during application request-processing configuration.
minimal APIused by · A minimal API is an ASP.NET Core programming model for defining HTTP endpoints with minimal framework ceremony, typically without controller classes.
WebApplicationuses · WebApplication is an ASP.NET Core application type that hosts configured services, runs the web server, and exposes the HTTP request-processing pipeline.

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.