How deeply does ASP.NET Core in Action, 3e cover 405 Method Not Allowed?

Explains route-and-verb matching and troubleshooting, but does not descend into response-generation internals.

405 Method Not Allowed

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

A 405 status code is an HTTP response status indicating that the request method is not supported for the targeted resource.

A 405 response means that a request reached a matching resource path, but its HTTP method is not supported there. The endpoint handler does not run. section 5.2.2 section 20.3.3

Check these common causes when a request returns 405:

Use the HTTP verb assigned to the endpoint, such as GET, POST, PUT, or DELETE. section 5.2.2 section 20.3.3
Verify the URL path carefully; a typo can produce 405 even when the intended verb is correct. section 5.2.2
Match controller actions with attributes such as [HttpGet] and [HttpPost], or map the corresponding minimal API verb. section 20.3.3 section 5.2.2

A wrong verb

An endpoint mapped with MapGet("/person/{name}", handler) accepts GET requests. Sending POST to /person/Al matches the path but not the method, so the handler is skipped and the response is 405 Method Not Allowed. 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.

Use the endpoint map to compare HTTP verbs with their intended operations, including fetching, creating, replacing, modifying, and deleting resources. section 5.2.2

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

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Related concepts

HTTP response codekind of · An HTTP status code is a standardized three-digit value in an HTTP response that indicates the outcome of processing the corresponding request.
HTTP methodproduced by · An HTTP method is a standardized operation token in an HTTP request that specifies the intended action on a resource.
HTTP 404 errorcontrasts with · An HTTP 404 Not Found response indicates that the server did not find a current representation of the requested resource or is unwilling to disclose that one exists.
request messageproduced by · An HTTP request is a message sent by a client to a server that specifies a method and target and may include headers and a body.
deletioncontrasts with · Deletion is an operation that removes an item, association, or resource from a collection or system, or requests or marks it for removal.

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.