MVC缓存02,使用数据层缓存,添加或修改时让缓存失效

2021-08-15 22:12:21

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);

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□ 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

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

码农公寓

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