数据缓存.NET 4.0 MemoryCache with SqlChangeMonitor

ALTER DATABASE database_name SET TRUSTWORTHY ON WITH ROLLBACK IMMEDIATE
GO
ALTER DATABASE database_name SET ENABLE_BROKER WITH ROLLBACK IMMEDIATE
GO
ALTER AUTHORIZATION ON DATABASE::database_name TO sa

public class UserDal
{
public List<UserInfo> GetModelList()
{
const string Users = "Users";
List<UserInfo> list = null;
if (MemoryCache.Default.Contains("Users") == false)
{
list = new List<UserInfo>();
CacheItemPolicy policy = new CacheItemPolicy();//缓存过期策略
string connStr = ConfigurationManager.ConnectionStrings["MyDatabaseConnection"].ConnectionString;

SqlDependency.Start(connStr);//必须先调用，否则无法执行Sql命令

using (SqlConnection conn = new SqlConnection(connStr))
{
//注意：sql语句中必须要指名查询的字段名，不能使用*号，并且表名必须的为：dbo.表名，否则缓存无效
using (SqlCommand command = new SqlCommand("select Username,DisplayName from dbo.users", conn))
{
command.Notification = null;
SqlDependency dep = new SqlDependency();//Sql依赖命令
dep.AddCommandDependency(command);//建立依赖关系
conn.Open();
using(IDataReader reader = command.ExecuteReader())//必须执行一次命令，否则无法注册通知
{
while (reader.Read())
{
list.Add(BindingReader(reader));
}
}
SqlChangeMonitor monitor = new SqlChangeMonitor(dep);
policy.ChangeMonitors.Add(monitor);//如果数据库表更改，策略使将缓存数据从缓存中移除
}
}
MemoryCache.Default.Add("Users", list, policy);
//MemoryCache.Default.Set(Users, list, policy);
}
else
{
list = MemoryCache.Default.Get(Users) as List<UserInfo>;
if (list.FirstOrDefault(m=>m.UserName=="system") ==null)
{
list.Add(new UserInfo { UserName = "system", DisplayName = "缓存" });
}
}
return list;
}

private UserInfo BindingReader(IDataReader reader)
{
UserInfo model = new UserInfo();
model.UserName = reader["UserName"].ToString();
model.DisplayName = reader["DisplayName"].ToString();
return model;
}

}