Asp.NET MVC Widget开发 - ViewEngine

在Asp.NET开发博客类系统，我们经常都会用到Widget，像在线好友、最近访问好友、最新留言等，关于Asp.NET MVC与Asp.NET视图的差异，这里不再说了，大家可去查一下，接下来我以“我的好友”列表来要介绍在Asp.NET MVC实现这一功能以及结构设计。

• 开发工具：VS 2010 EN
• 开发语言：Visual C#
• ASP.NET MVC 3

1. Asp.NET MVC Widget - 设计
2. Asp.NET MVC Widget - Controller控制器
3. Asp.NET MVC Widget - ViewEngine
4. Asp.NET MVC Widget - Mobile支持
5. Asp.NET MVC Widget - Html.Widget扩展方法

关于ViewEngine这篇是Widgets实现的核心，这里需要自定义Asp.NET MVC的视图引擎，也就是让Asp.NET MVC视图引擎可以找到widgets中的文件。

直接访问会出现以下错误，提示找不到显示文件

由错误中也可以看到 Asp.NET MVC默认引擎搜索文件的目录

/Views/Widget/

/Views/Shared/

要寻找到"widgets"中的文件就必须要让视图引擎去"widgets"中搜索文件

如Friends: /widgets/Friends/

添加自定义视图引擎

1. 添加 "WidgetViewEngine.cs"，继承自BuildManagerViewEngine

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace Widgets
{
    public class WidgetViewEngine : BuildManagerViewEngine
    {
        internal static readonly string ViewStartFileName = "_ViewStart";

        public WidgetViewEngine()
            : this(null)
        {
        }

        public WidgetViewEngine(IViewPageActivator viewPageActivator)
            : base(viewPageActivator)
        {
            AreaViewLocationFormats = new[] {
                "~/Areas/{2}/Views/{1}/{0}.cshtml",
                "~/Areas/{2}/Views/Shared/{0}.cshtml"
            };
            AreaMasterLocationFormats = new[] {
                "~/Areas/{2}/Views/{1}/{0}.cshtml",
                "~/Areas/{2}/Views/Shared/{0}.cshtml"
            };
            AreaPartialViewLocationFormats = new[] {
                "~/Areas/{2}/Views/{1}/{0}.cshtml",
                "~/Areas/{2}/Views/Shared/{0}.cshtml"
            };

            ViewLocationFormats = new[] {
                "~/Views/{1}/{0}.cshtml",
                "~/Views/Shared/{0}.cshtml"

            };
            MasterLocationFormats = new[] {
                "~/Views/{1}/{0}.cshtml",
                "~/Views/Shared/{0}.cshtml"
            };
            PartialViewLocationFormats = new[] { 
                "~/{1}s/{0}/Widget.cshtml",
                "~/Views/{1}/{0}.cshtml",
                "~/Views/Shared/{0}.cshtml"
            };

            FileExtensions = new[] {
                "cshtml"
            };
        }

        protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
        {
            return new RazorView(controllerContext, partialPath,
                                 layoutPath: null, runViewStartPages: false, viewStartFileExtensions: FileExtensions, viewPageActivator: ViewPageActivator);
        }

        protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
        {
            var view = new RazorView(controllerContext, viewPath,
                                     layoutPath: masterPath, runViewStartPages: true, viewStartFileExtensions: FileExtensions, viewPageActivator: ViewPageActivator);
            return view;
        }
    }
}

2. 添加AppStart_Widgets.cs，修改默认视图引擎

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Widgets;

[assembly: PreApplicationStartMethod(typeof(AppStart_Widgets), "Start")]

namespace Widgets
{
    public class AppStart_Widgets
    {
        public static void Start()
        {
            // Clear system default view engines
            ViewEngines.Engines.Clear();
            ViewEngines.Engines.Add(new WidgetViewEngine());
        }
    }
}

3. 添加Friend实体及测试数据

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Widgets.Models
{
    public class Friend
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    public class FriendsContext
    {
        public FriendsContext()
        {
            Friends = new List<Friend>() { 
                new Friend{Id=1,Name="zhang san"},
                new Friend{Id=2,Name="li si"},
                new Friend{Id=3,Name="wang wu"}
            };
        }

        public IEnumerable<Friend> Friends { get; private set; }
    }
}

4. 更改widgets/Friends/Widget.cshtml

@model IEnumerable<Widgets.Models.Friend>
@{
    Layout = "~/widgets/_Layout.cshtml";
    ViewBag.Title = "My friends";
}
<div class="newsletter">
    <ul>
        @foreach (var item in Model)
        {
            <li>@item.Name</li>
        }
    </ul>
</div>

项目结构

其它代码详见源码中。

再次访问，便出现要的结果。

源码下载