自定义MVC视图引擎ViewEngine 创建Model的专属视图

MVC内置的视图引擎有WebForm view engine和Razor view engine，当然也可以自定义视图引擎ViewEngine。本文想针对某个Model，自定义该Model的专属视图。

□ 思路

1、控制器方法返回ActionResult是一个抽象类
2、ActionResult的其中一个子类ViewResult，正是她使用IView实例最终渲染出视图
3、需要自定义IView
4、IViewEngine管理着IView，同时也需要自定义IViewEngine
5、自定义IViewEngine是需要全局注册的

□ IView接口

public interface IView
{
    void Render(System.Web.Mvc.ViewContext viewContext, System.IO.TextWriter writer)
}

第一个参数ViewContext包含了需要被渲染的信息，被传递到前台的强类型Model也包含在其中。
第二个参数TextWriter可以帮助我们写出想要的html格式。

□ IViewEngine接口

public interface IViewEngine
{
    System.Web.Mvc.ViewEngineResult FindPartialView(System.Web.Mvc.ControllerContext controllerContext, string partialViewName, bool useCache);
    System.Web.Mvc.ViewEngineResult FindView(System.Web.Mvc.ControllerContext controllerContext, string viewName, string masterName, bool useCache);
    void ReleaseView(System.Web.Mvc.ControllerContext controllerContext, System.Web.Mvc.IView view);
}

FindPartialView:在当前控制器上下文ControllerContext中找到部分视图。
FindView：在当前控制器上下文ControllerContext中找到视图。
ReleaseView：释放当前控制器上下文ControllerContext中的视图。

  模拟一个Model和数据服务类

   public class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Score { get; set; }
    }

    public class DataAccess
    {
        List<Student> students = new List<Student>();

        public DataAccess()
        {
            for (int i = 0; i < 10; i++)
            {
                students.Add(new Student
                {
                    Id = i + 1,
                    Name = "Name" + Convert.ToString(i+1),
                    Score = i + 80
                });
            }
        }

        public List<Student> GetStudents()
        {
            return students;
        }
    }

  实现IView接口，自定义输出html格式

using System.Collections.Generic;
using System.Web.Mvc;
using CustomViewEngine.Models;

namespace CustomViewEngine.Extension
{
    public class StudentView : IView
    {

        public void Render(ViewContext viewContext, System.IO.TextWriter writer)
        {
            //从视图上下文ViewContext中拿到model
            var model = viewContext.ViewData.Model;
            var students = model as List<Student>;

            //自定义输出视图的html格式
            writer.Write("<table border=1><tr><th>编号</th><th>名称</th><th>分数</th></tr>");
            foreach (Student stu in students)
            {
                writer.Write("<tr><td>" + stu.Id + "</td><td>" + stu.Name + "</td><td>" + stu.Score + "</td></tr>");
            }
            writer.Write("</table>");
        }
    }
}

  实现IViewEngine，返回自定义IView

using System;
using System.Web.Mvc;

namespace CustomViewEngine.Extension
{
    public class StudentViewEngine : IViewEngine
    {

        public ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache)
        {
            throw new System.NotImplementedException();
        }

        public ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache)
        {
            if (viewName == "StudentView")
            {
                return new ViewEngineResult(new StudentView(), this);
            }
            else
            {
                return new ViewEngineResult(new String[]{"针对Student的视图还没创建！"});
            }
        }

        public void ReleaseView(ControllerContext controllerContext, IView view)
        {

        }
    }
}

  HomeController

using System.Web.Mvc;
using CustomViewEngine.Models;

namespace CustomViewEngine.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            var students = new DataAccess().GetStudents();
            ViewData.Model = students;
            return View("StudentView");
        }

    }
}

  全局注册

    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            WebApiConfig.Register(GlobalConfiguration.Configuration);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            ViewEngines.Engines.Add(new StudentViewEngine());
        }
    }

浏览/Home/Index效果：