路由与动作选择.docxVIP

【ASP.NET Web API教程】4.2 路由与动作选择注：本文是【ASP.NET Web API系列教程】的一部分，如果您是第一次看本系列教程，请先看前面的内容。4.2 Routing and Action Selection4.2 路由与动作选择本文引自：/web-api/overview/web-api-routing-and-actions/routing-and-action-selectionBy Mike Wasson | July 27, 2012作者：Mike Wasson | 日期：2012-7-27This article describes how ASP.NET Web API routes an HTTP request to a particular action on a controller.本文描述ASP.NET Web API如何把一个HTTP请求路由到控制器的一个特定的方法上。For a high-level overview of routing, see Routing in ASP.NET Web API.关于路由的总体概述，参阅“ASP.NET Web API中的路由”（本系列教程的前一小节 — 译者注）。This article looks at the details of the routing process. If you create a Web API project and find that some requests don’t get routed the way you expect, hopefully this article will help.本文考察路由过程的细节。如果你创建了一个Web API项目，并发现有些请求并未按你期望的方式被路由，希望这篇文章对你会有所帮助。Routing has three main phases:路由有三个主要阶段：Matching the URI to a route template.将URI匹配到一个路由模板。Selecting a controller.选择一个控制器Selecting an action.选择一个动作。You can replace some parts of the process with your own custom behaviors. In this article, I describe the default behavior. At the end, I note the places where you can customize the behavior.你可以用自己的自定义行为来替换这一过程的某些部分。在本文中，我会描述默认行为。最后，我会注明可以在什么地方自定义行为。Route Templates路由模板A route template looks similar to a URI path, but it can have placeholder values, indicated with curly braces:路由模板看上去类似于一个URI路径，但它可以具有占位符，这是用花括号来指示的：api/{controller}/public/{category}/{id}When you create a route, you can provide default values for some or all of the placeholders:当创建一条路由时，可以为某些或所有占位符提供默认值：defaults: new { category = all }You can also provide constraints, which restrict how a URI segment can match a placeholder:也可以提供约束，它限制URI片段如何与占位符匹配：constraints: new { id = @\d+ } // Only matches if id is one or more digits.// 用正则表达式限制片段的取值，上语句表明，id片段的值必须是一个或多个数字。// 因此，URI中id片段必须是数字才能与这条路由匹配The framework tries to match the segments in the URI path to the template. Literals in the template must match exactly. A placeholder matches any value, unless you specify constraints. The framew