在我们新建一个Web API项目时，会在App_Start文件夹下的WebApiConfig.cs中定义一个默认路由：
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
在默认路由中加入“api”是为了避免与ASP.NET MVC的路由冲突。当然如果你不喜欢这个约定，可以修改默认路由。
路由匹配规则：{controller}和{id}略过，只介绍action的匹配。
1.Web API首先根据HTTP方法名寻找命名以HTTP方法名开头的action。举例：
public class ProductsController : ApiController
{
public void GetAllProducts() { }
public IEnumerable<Product> GetProductById(int id) { }
public HttpResponseMessage DeleteProduct(int id){ }
}
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" 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2.但是上面的约定只适用于GET、POST、PUT和DELETE方法。其他的HTTP方法可以使用AcceptVerbs attribute匹配，前面的四种方法亦同样适用。举例：
public class ProductsController : ApiController
{
[HttpGet]
public Product FindProduct(id) {}
}
public class ProductsController : ApiController
{
[AcceptVerbs("GET", "HEAD")]
public Product FindProduct(id) { } // WebDAV method
[AcceptVerbs("MKCOL")]
public void MakeCollection() { }
}
3.根据action名匹配（重写路由）。举例：
routes.MapHttpRoute(
name: "ActionApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);
3.1.根据上面的路由规则“api/products/details/1”的GET请求将会匹配：
public class ProductsController : ApiController
{
[HttpGet]
public string Details(int id);
}
3.2.可以使用ActionName attribute重写action名。举例：
public class ProductsController : ApiController
{
[HttpGet]
[ActionName("Thumbnail")]
public HttpResponseMessage GetThumbnailImage(int id); [HttpPost]
[ActionName("Thumbnail")]
public void AddThumbnailImage(int id);
}
这样"api/products/thumbnail/id”就有两个匹配，分别对应GET和POST。
4.如果一个方法不想被当作action调用，可以使用NonAction attribute，举例：
// Not an action method.
[NonAction]
public string GetPrivateData() { ... }