如何使用自定义的约束，在ASP.NET MVC路由一个HttpMethodConstraint？ [英] How do I use a custom constraint with a HttpMethodConstraint in ASP.NET MVC routing?

问题描述

我有一个控制器，只接受POST这个网址：

I have a controller that only accepts a POST on this URL:

POST http://server/stores/123/products

应将有关内容类型应用程序/ JSON 的，所以这是我在我的路由表：

The POST should be of content-type application/json, so this is what I have in my routing table:

routes.MapRoute(null,
                "stores/{storeId}/products",
                new { controller = "Store", action = "Save" },
                new {
                      httpMethod = new HttpMethodConstraint("POST"),
                      json = new JsonConstraint()
                    }
               );

其中， JsonConstraint 是：

public class JsonConstraint : IRouteConstraint
{
    public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
    {
        return httpContext.Request.ContentType == "application/json";
    }
}

当我使用的路线，我得到一个405禁止访问：

When I use the route, I get a 405 Forbidden:

用于访问路径/存储/ 123 /产品'是不允许的HTTP动词POST

不过，如果我删除 JSON =新JsonConstraint（）约束，它工作正常。有谁知道我做错了吗？

However, if I remove the json = new JsonConstraint() constraint, it works fine. Does anybody know what I'm doing wrong?

推荐答案

我把这个注释，但没有足够的空间。

I'd put this in a comment but there isn't enough space.

在编写自定义约束它要检查 routeDirection 参数，并确保你的逻辑只运行在正确的时间非常重要。

When writing a custom constraint it is very important to inspect the routeDirection parameter and make sure that your logic runs only at the right time.

这参数告诉你你的约束是否正在运行，而处理传入的请求或被运行，而有人正在生成一个URL（例如，当他们叫 Html.ActionLink ）

That parameter tells you whether your constraint is being run while processing an incoming request or being run while someone is generating a URL (such as when they call Html.ActionLink).

在你的情况我想你想要把所有的匹配code在一个巨大的如果：

In your case I think you want to put all your matching code in a giant "if":

public bool Match(HttpContextBase httpContext, Route route,
    string parameterName, RouteValueDictionary values,
    RouteDirection routeDirection) 
{
    if (routeDirection == RouteDirection.IncomingRequest) {
        // Only check the content type for incoming requests
        return httpContext.Request.ContentType == mimeType; 
    }
    else {
        // Always match when generating URLs
        return true;
    }
}

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