MVC缓存02,使用数据层缓存,添加或修改时让缓存失效

在"MVC缓存01,使用控制器缓存或数据层缓存"中，在数据层中可以设置缓存的有效时间。但这个还不够"智能"，常常希望在编辑或创建的时候使缓存失效，加载新的数据。

□ 思路

1、缓存是以键值<string, object>存放的，在创建缓存的时候，先把IDictionary<int,T>作为缓存内容存储,int为T的主键。

2、EF上下文保存的时候时候把变化保存到数据库，并更新缓存中的内容。

● 先找出上下文中状态为added或modified的实体：var changeobjects
● 把变化保存数据到数据库：context.SaveChanges()
● 根据缓存key获取类型为IDictionary<int,T>的缓存内容：var cacheData = Cache.Get("vehicles") as Dictionary<int, Vehicle>;
● 最后遍历这些变化的实体，更新缓存项：cacheData[vehicle.Id] = vehicle;

□ 缓存接口

    public interface ICacheProvider
    {
        object Get(string key);
        void Set(string key, object data, int cacheTime);
        bool IsSet(string key);
        void Invalidate(string key);
    }

□ 缓存接口实现

围绕using System.Runtime.Caching的MemoryCache.Default返回类型为ObjectCache的缓存属性实现缓存接口：获取缓存项、设置缓存、判断是否设置缓存、清空缓存。

using System;
using System.Runtime.Caching;

namespace MvcApplication1.Cache
{
    public class DefaultCacheProvider : ICacheProvider
    {
        private ObjectCache Cache
        {
            get { return MemoryCache.Default; }
        }
        public object Get(string key)
        {
            return Cache[key];
        }

        public void Set(string key, object data, int cacheTime)
        {
            CacheItemPolicy policy = new CacheItemPolicy();
            policy.AbsoluteExpiration = DateTime.Now + TimeSpan.FromMinutes(cacheTime);
            Cache.Add(new CacheItem(key, data), policy);
        }

        public bool IsSet(string key)
        {
            return (Cache[key] != null);
        }

        public void Invalidate(string key)
        {
            Cache.Remove(key);
        }
    }
}

□ Model

    public partial class Vehicle
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }

□ 针对Vehicle的Repositoy接口：

using System.Collections.Generic;
using MvcApplication1.Models;

namespace MvcApplication1.Repository
{
    public interface IVehicleRepository
    {
        void ClearCache();
        IEnumerable<Vehicle> GetVehicles();
        void Insert(Vehicle vehicle);
        void Update(Vehicle vehicle);
        void SaveChanges();
    }
}

□ 针对Vehicle的Repositoy接口实现：  

using System.Collections.Generic;
using System.Data;
using System.Data.Entity.Infrastructure;
using System.Linq;
using MvcApplication1.Cache;
using MvcApplication1.Models;
namespace MvcApplication1.Repository
{
    public class VehicleRepository : IVehicleRepository
    {
        protected DemoEntities DataContext { get; private set; }
        public ICacheProvider Cache { get; set; }

        public VehicleRepository() : this(new DefaultCacheProvider())
        {

        }

        public VehicleRepository(ICacheProvider cacheProvider)
        {
            this.DataContext = new DemoEntities();
            this.Cache = cacheProvider;
        }

        public void ClearCache()
        {
            Cache.Invalidate("vehicles");
        }

        public System.Collections.Generic.IEnumerable<Models.Vehicle> GetVehicles()
        {
            var vehicles = Cache.Get("vehicles") as IDictionary<int, Vehicle>;
            if (vehicles == null)
            {
                vehicles = DataContext.Vehicle.ToDictionary(v => v.Id);
                if (vehicles.Any())
                {
                    Cache.Set("vehicles",vehicles,30);
                }
            }
            return vehicles.Values;
        }

        public void Update(Vehicle vehicle)
        {
            if (vehicle != null)
            {
                DataContext.Set<Vehicle>().Attach(vehicle);
                DataContext.Entry(vehicle).State = EntityState.Modified;
            }
        }

        public void Insert(Vehicle vehicle)
        {
            DataContext.Set<Vehicle>().Add(vehicle);
        }

        public void SaveChanges()
        {
            //获取上下文中EntityState状态为added或modified的Vehicle
             var changeobjects = DataContext.ChangeTracker.Entries<Vehicle>();

            //把变化保存到数据库
            DataContext.SaveChanges();

            //更新缓存中相关的Vehicle
            var cacheData = Cache.Get("vehicles") as Dictionary<int, Vehicle>;
            if (cacheData != null)
            {
                foreach (var item in changeobjects)
                {
                    var vehicle = item.Entity as Vehicle;
                    cacheData[vehicle.Id] = vehicle;
                }
            }
        }
    }
}

在保存缓存Cache.Set("vehicles",vehicles,30)之前，把从上下文获取到的数据转换成IDictionary<int,T>类型vehicles = DataContext.Vehicle.ToDictionary(v => v.Id);

□ HomeController

using System.Linq;
using System.Web;
using System.Web.Mvc;
using MvcApplication1.Models;
using MvcApplication1.Repository;

namespace MvcApplication1.Controllers
{
    public class HomeController : Controller
    {
        public IVehicleRepository Repository { get; set; }

        public HomeController(IVehicleRepository repository)
        {
            this.Repository = repository;
        }

        public HomeController() : this(new VehicleRepository())
        {

        }
        public ActionResult Index()
        {
            return View(Repository.GetVehicles());
        }

        [HttpPost]
        public ActionResult Index(FormCollection form)
        {
            Repository.ClearCache();
            return RedirectToAction("Index");
        }

        public ActionResult Edit(int id)
        {
            var vehicle = Repository.GetVehicles().Single(v => v.Id == id);
            return View(vehicle);
        }

        [HttpPost]
        public ActionResult Edit(Vehicle vehicle)
        {
            Repository.Update(vehicle);
            Repository.SaveChanges();
            return RedirectToAction("Index");
        }

        public ActionResult Create()
        {
            return View(new Vehicle());
        }

        [HttpPost]
        public ActionResult Create(Vehicle vehicle)
        {
            Repository.Insert(vehicle);
            Repository.SaveChanges();
            return RedirectToAction("Index");
        }
    }
}

□ Home/Index.cshtml

@model IEnumerable<MvcApplication1.Models.Vehicle>

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<style type="text/css">
    table td {
        border-collapse: collapse;
        border: solid 1px black;
    }


</style>

<table cellpadding="0" cellspacing="0" border="0">
    <tr>
        <th>编号</th>
        <th>车型</th>
        <th>价格</th>
        <th></th>
    </tr>
    @foreach (var vehicle in Model)
    {
        <tr>
            <td>@vehicle.Id.ToString()</td>
            <td>@vehicle.Name</td>
            <td>@string.Format("{0:c}",vehicle.Price)</td>
            <td>
            @Html.ActionLink("编辑", "Edit", new { id=vehicle.Id })
        </td>
        </tr>
    }
</table>

@using (Html.BeginForm())
{
    <input type="submit" value="使缓存失效重新获取数据库数据" id="InvalidButton" name="InvalidButton"/>
}

<p>
    @Html.ActionLink("创建", "Create")
</p>

□ Home/Create.cshtml

@model MvcApplication1.Models.Vehicle

@{
    ViewBag.Title = "Create";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Create</h2>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Vehicle</legend>

        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Price)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Price)
            @Html.ValidationMessageFor(model => model.Price)
        </div>

        <p>
            <input type="submit" value="Create" />
        </p>
    </fieldset>
}

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

□ Home/Edit.cshtml

@model MvcApplication1.Models.Vehicle

@{
    ViewBag.Title = "Edit";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Edit</h2>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Vehicle</legend>

        @Html.HiddenFor(model => model.Id)

        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Price)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Price)
            @Html.ValidationMessageFor(model => model.Price)
        </div>

        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}


@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

 

□ 结果：

创建或修改之前：

 

编辑更新：

 

创建：

 

编辑创建成功后：

 

□ 参考资料
※ DATA CACHING WITH .NET 4.0 AND ASP.NET MVC – PART 2