ASP.NET MVC中的各种上下文对象

先来个图预览一下：

1.首先是System.Web.Routing下的RequestContext类，代码相当简单，把HttpContextBase和RouteData放在一起就OK了。

using System;
using System.Security.Permissions;
using System.Web;

namespace System.Web.Routing
{
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal),
     AspNetHostingPermission(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
    public class RequestContext
    {
        // Methods
        public RequestContext(HttpContextBase httpContext, RouteData routeData)
        {
            if (httpContext == null)
                throw new ArgumentNullException("httpContext");
            if (routeData == null)
                throw new ArgumentNullException("routeData");
            this.HttpContext = httpContext;
            this.RouteData = routeData;
        }

        // Properties
        public HttpContextBase HttpContext { get; internal set; }

        public RouteData RouteData { get; internal set; }
    }
}

关于RouteData，我以后会讲的，现在只需要知道它存储了Route信息，从URL中根据Route规则Map到的参数值都在里面。

2.接着就是ControllerContext类了，这个类很有意思：

using System.Security.Permissions;

namespace System.Web.Mvc
{
    using System.Web.Routing;

    [AspNetHostingPermission(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
    public class ControllerContext : RequestContext
    {
        protected internal ControllerContext(ControllerContext controllerContext)
            : this(GetControllerContext(controllerContext), GetControllerContext(controllerContext).Controller) {}

        public ControllerContext(HttpContextBase httpContext, RouteData routeData, ControllerBase controller)
            : base(httpContext, routeData)
        {
            if (controller == null) throw new ArgumentNullException("controller");
            Controller = controller;
        }

        public ControllerContext(RequestContext requestContext, ControllerBase controller)
            : this(
                GetRequestContext(requestContext).HttpContext, GetRequestContext(requestContext).RouteData, controller) {}

        public ControllerBase Controller { get; private set; }

        internal static RequestContext GetRequestContext(RequestContext requestContext)
        {
            if (requestContext == null) throw new ArgumentNullException("requestContext");
            return requestContext;
        }

        internal static ControllerContext GetControllerContext(ControllerContext controllerContext)
        {
            if (controllerContext == null) throw new ArgumentNullException("controllerContext");
            return controllerContext;
        }
    }
}

其实它也就是在RequestContext的基础上加了个对Controller的引用（当然是对ControllerBase基类的引用）。

它的几个重载的构造函数以及静态方法写得很有意思，值得借鉴。

3.