基于SqlDependency的Asp.net数据缓存

首先，确保目标数据库的is_broker_enabled已经enabled。

SELECT name, is_broker_enabled FROM sys.databases

如果不是enabled，使用以下语句

ALTER DATABASE DB_Name SET ENABLE_BROKER
GO

使用以下语句授权指定用户订阅Query Notifications

GRANT SUBSCRIBE QUERY NOTIFICATIONS TO "domain name\user name"

以下是c# 源码

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Web.Caching;

public class WebCacheHelper<T> where T : class
{
    public event FetchDataFromDBHandler<T> OnFetchDataFromDB;

    public T GetFromCache(string connectionString, string tableName, string cacheKey)
    {
        var cache = HttpRuntime.Cache;
        T data = null;

        if (cache[cacheKey] != null)
        {
            return cache[cacheKey] as T;
        }

        using (SqlConnection con = new SqlConnection(connectionString))
        using (SqlCommand cmd =
            new SqlCommand(string.Format("select 1 from dbo.{0}", tableName)
                , con))
        {
            bool started = SqlDependency.Start(connectionString);

            con.Open();
            cmd.Notification = null;
            cmd.NotificationAutoEnlist = true;

            SqlCacheDependencyAdmin.EnableNotifications(connectionString);
            if (!SqlCacheDependencyAdmin.GetTablesEnabledForNotifications(
                connectionString).Contains(tableName))
            {
                SqlCacheDependencyAdmin.EnableTableForNotifications(connectionString, tableName);
            }

            SqlCacheDependency dependency = new SqlCacheDependency(cmd);

            if (OnFetchDataFromDB != null)
                data = OnFetchDataFromDB(started);

            cache.Insert(cacheKey, data, dependency);

            cmd.ExecuteNonQuery();
        }

        return data;
    }
}

public delegate T FetchDataFromDBHandler<T>(bool IsSqlDependecyStarted);

Sample

　　　　public class Movie
    {
        public int ID { get; set; }
        public string Title { get; set; }

        [Display(Name = "Release Date")]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        public DateTime ReleaseDate { get; set; }

        public string Genre { get; set; }
        public decimal Price { get; set; }
    }

    public class MovieDBContext : DbContext
    {
        public DbSet<Movie> Movies { get; set; }
    }

　　　　public class MovieController : Controller
    {
        private MovieDBContext db = new MovieDBContext();

        public ActionResult List()
        {
            WebCacheHelper<IEnumerable<Movie>> helper = new WebCacheHelper<IEnumerable<Movie>>();
            helper.OnFetchDataFromDB += x =>
            {
                var query = from p in db.Movies
                            select p;
                ViewBag.DataInitilized = "Cache data initialized at " + DateTime.Now.ToLongTimeString();
                ViewBag.DependencyStarted = x;
                return query.ToList();
            };
            var model = helper.GetFromCache(db.Database.Connection.ConnectionString, "Movies", "Movie");
            return View(model);
        }
　　　　}

SQL Server2008实测运行成功。 C#代码执行以后，数据库中将自动生成一个名为AspNet_SqlCacheTablesForChangeNotification的表。

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