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
展开
□ Home/Edit.cshtml
□ 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