MVC缓存02,使用数据层缓存,添加或修改时让缓存失效_.NET_编程开发_程序员俱乐部

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

class="alt">    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

logs_code_Collapse">展开@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

展开@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