ASP.NET MVC出来这么久了,心中却又很多的疑惑:为什么所有的View都要放在Views目录下? 为什么Shared文件夹下面的页面可以被共享? 为什么Page既可以是*.cshtml,也可以是*.aspx?
其实上面的几个问题归结起来都是视图引擎的功效。
在传统的ASP.NET中,可能还没有ViewEngine的概念。因为在Web From里面,实现Page实现了IHttpHanlder的接口,所以Page既是响应的处理类,也是视图的渲染类。在ASP.NET MVC中,视图的概念被抽象了出来,试图引擎的概念也被抽象成了一个接口。
首先来看一下IViewEngine接口的定义:
namespace System.Web.Mvc { public interface IViewEngine { ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache); ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache); void ReleaseView(ControllerContext controllerContext, IView view); } }
默认情况下,ASP.NET MVC提供了两个视图引擎:WebFormViewEngine和RazorViewEngine。
namespace System.Web.Mvc { public static class ViewEngines { private static readonly ViewEngineCollection _engines = new ViewEngineCollection { new WebFormViewEngine(), new RazorViewEngine(), }; public static ViewEngineCollection Engines { get { return _engines; } } } }
那为什么所有的视图都要放在Views目录下呢,这个就要拜RazorViewngines所赐了。
下面是RazorViewEngine的构造函数:
public RazorViewEngine(IViewPageActivator viewPageActivator) : base(viewPageActivator) { AreaViewLocationFormats = new[] { "~/Areas/{2}/Views/{1}/{0}.cshtml", "~/Areas/{2}/Views/{1}/{0}.vbhtml", "~/Areas/{2}/Views/Shared/{0}.cshtml", "~/Areas/{2}/Views/Shared/{0}.vbhtml" }; AreaMasterLocationFormats = new[] { "~/Areas/{2}/Views/{1}/{0}.cshtml", "~/Areas/{2}/Views/{1}/{0}.vbhtml", "~/Areas/{2}/Views/Shared/{0}.cshtml", "~/Areas/{2}/Views/Shared/{0}.vbhtml" }; AreaPartialViewLocationFormats = new[] { "~/Areas/{2}/Views/{1}/{0}.cshtml", "~/Areas/{2}/Views/{1}/{0}.vbhtml", "~/Areas/{2}/Views/Shared/{0}.cshtml", "~/Areas/{2}/Views/Shared/{0}.vbhtml" }; ViewLocationFormats = new[] { "~/Views/{1}/{0}.cshtml", "~/Views/{1}/{0}.vbhtml", "~/Views/Shared/{0}.cshtml", "~/Views/Shared/{0}.vbhtml" }; MasterLocationFormats = new[] { "~/Views/{1}/{0}.cshtml", "~/Views/{1}/{0}.vbhtml", "~/Views/Shared/{0}.cshtml", "~/Views/Shared/{0}.vbhtml" }; PartialViewLocationFormats = new[] { "~/Views/{1}/{0}.cshtml", "~/Views/{1}/{0}.vbhtml", "~/Views/Shared/{0}.cshtml", "~/Views/Shared/{0}.vbhtml" }; FileExtensions = new[] { "cshtml", "vbhtml", }; }
好了,找了“罪魁祸首”,就好好地调教一个,让它乖乖听话,小样让去哪就去哪里。
namespace MvcApplicatin.Web.Mvc.ViewEngine { public sealed class CustomViewEngine : RazorViewEngine { public CustomViewEngine() { ViewLocationFormats = new[] { "~/Views/{1}/{0}.cshtml", "~/Views/Shared/{0}.cshtml", "~/CustomViewLocation/{1}/{0}.cshtml" }; } public override ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache) { return base.FindView(controllerContext, viewName, masterName, useCache); } } }
接下去就很简单了,只需要把原来的视图引擎清空,加载自己的视图引擎就可以了。
protected void Application_Start() { AreaRegistration.RegisterAllAreas(); ViewEngines.Engines.Clear(); ViewEngines.Engines.Add(new CustomViewEngine()); RegisterGlobalFilters(GlobalFilters.Filters); RegisterRoutes(RouteTable.Routes); }