最近项目需要几秒就获取一次数据，查数据库服务器压力会很大，因此用缓存技术来缓解服务器压力。

使用SqlCacheDependency采用轮询的方式来获取缓存，SqlDependency查询通知的方式来更新缓存应该更好，先说轮询的方式吧。

配置文件如下：

<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
  <caching>
    <sqlCacheDependency enabled="true" pollTime="10000">
      <databases>
        <add name="msBaby" connectionStringName="conn"/>
      </databases>
    </sqlCacheDependency>
  </caching>
  </system.web>
  <connectionStrings>
    <add name="conn" connectionString="data source=SH-05\SA;initial catalog=Baby;user id=sa;password=123456;Asynchronous Processing=true;MultipleActiveResultSets=true;Integrated Security=True"/>
  </connectionStrings>
</configuration>

其中 connectionStringName="conn"是connectionStrings的name，name="msBaby" 中，msBaby就是数据库名称。

以下是代码示例：

基类

   public class BaseCache
    {
        private string connectionString = ConfigurationManager.ConnectionStrings["conn"].ConnectionString;

        /// <summary>
        /// 获取缓存数据
        /// </summary>
        /// <param name="cacheName">缓存名</param>
        /// <param name="dataBaseName">数据库名</param>
        /// <param name="tableName">表名</param>
        /// <returns></returns>
        public DataTable GetCacheData(string cacheName, string dataBaseName, string tableName)
        {
            DataTable data = http://www.mamicode.com/(DataTable)HttpRuntime.Cache[cacheName]; //获取缓存
            // 判断缓存数据为空  
            if (data =http://www.mamicode.com/= null)
            {
                // 获取数据  
                data = http://www.mamicode.com/GetDataSource();
                SqlCacheDependencyAdmin.EnableTableForNotifications(connectionString, tableName);
                SqlCacheDependency depend = new SqlCacheDependency(dataBaseName, tableName);
                HttpContext.Current.Cache.Insert(cacheName, data, depend);
            }
            return data;
        }

        public virtual DataTable GetDataSource()
        {
            return null;
        }
    }

数据库帮助类

  public class DBHelper
    {
        private static string connectionString = ConfigurationManager.ConnectionStrings["conn"].ConnectionString;

        public static DataTable GetData(string sql, params SqlParameter[] parameters)
        {
            DataTable data;
            try
            {
                SqlConnection conn = new SqlConnection(connectionString);
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(parameters);
                    SqlDataAdapter dataAdapter = new SqlDataAdapter(cmd);
                    data = http://www.mamicode.com/new DataTable();
                    dataAdapter.Fill(data);
                }
            }
            catch (Exception)
            {
                throw;
            }
            return data;
        }
    }

子类重写GetDataSource方法

  public class Job : BaseCache
    {
        public override DataTable GetDataSource()
        {
            return DBHelper.GetData("SELECT TOP 50 * FROM job");
        }
    }

外部类中调用

   Job job = new Job();

   DataTable dt = job.GetCacheData("jobCache", "msBaby", "job");

这里的msBaby与webconfig中相同，job是数据库表名称。

<databases>
        <add name="msBaby" connectionStringName="conn"/>
</databases>

SqlCacheDependency的使用