using System;
using System.Collections;
using System.Web;
using System.Web.Caching;
using System.Net;
using System.IO;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
namespace CacheManagement
{
public interface IWebCache
{
void Add(string key, object value);
object Get(string key);
void Remove(string key, bool useDependency);
}
public class WebCacheBase : IWebCache
{
protected bool CheckParameters(string key)
{
return !string.IsNullOrEmpty(key);
}
protected virtual CacheDependency GetCacheDependency(string key)
{
return null;
}
protected virtual void OnBeforeAdd(string key)
{
}
public virtual void Add(string key, object value)
{
if (!this.CheckParameters(key)) return;
this.OnBeforeAdd(key);
HttpRuntime.Cache.Insert(
key,
value,
this.GetCacheDependency(key),
System.Web.Caching.Cache.NoAbsoluteExpiration,
System.Web.Caching.Cache.NoSlidingExpiration,
System.Web.Caching.CacheItemPriority.Default,
null);
}
public virtual object Get(string key)
{
if (!this.CheckParameters(key)) return null;
return HttpRuntime.Cache.Get(key);
}
public virtual void Remove(string key, bool useDependency)
{
if (!this.CheckParameters(key)) return;
HttpRuntime.Cache.Remove(key);
}
}
public class SqlDependencyWebCache : WebCacheBase
{
private string _connectionString;
private SqlConnection GetConnection()
{
return new SqlConnection(this._connectionString);
}
private SqlCommand GetSelectCommand(string key)
{
SqlConnection conn = this.GetConnection();
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select Flag from dbo.CacheDependency where CacheKey=@CacheKey";
SqlParameter sqlParam = cmd.Parameters.Add("@CacheKey", SqlDbType.VarChar, 50);
sqlParam.Value = key;
return cmd;
}
private SqlCommand GetUpdateCommand(string key)
{
SqlConnection conn = this.GetConnection();
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = @"
if exists (select 1 from dbo.CacheDependency where CacheKey=@CacheKey)
update dbo.CacheDependency set Flag=case when isnull(flag,0)=0 then 1 else 1 end where CacheKey=@CacheKey
else
insert into dbo.CacheDependency (CacheKey,Flag)
values (@CacheKey, 0)
";
SqlParameter sqlParam = cmd.Parameters.Add("@CacheKey", SqlDbType.VarChar, 50);
sqlParam.Value = key;
return cmd;
}
private void UpdateCacheDependency(string key)
{
SqlCommand cmd = this.GetUpdateCommand(key);
using (cmd.Connection)
{
cmd.Connection.Open();
cmd.Prepare();
cmd.ExecuteNonQuery();
}
}
protected override void OnBeforeAdd(string key)
{
this.UpdateCacheDependency(key);
}
protected override CacheDependency GetCacheDependency(string key)
{
SqlCommand cmd = this.GetSelectCommand(key);
SqlCacheDependency sqlCacheDependency = new SqlCacheDependency(cmd);
using (cmd.Connection)
{
cmd.Connection.Open();
cmd.Prepare();
cmd.ExecuteNonQuery();
}
return sqlCacheDependency;
}
public SqlDependencyWebCache(string connectionString)
{
this._connectionString = connectionString;
}
public override void Remove(string key, bool useDependency)
{
if (!this.CheckParameters(key)) return;
if (useDependency)
{
this.UpdateCacheDependency(key);
}
else
{
base.Remove(key, useDependency);
}
}
}
public class WebCacheFactory
{
public static IWebCache GetWebCache()
{
string connectionString = ConfigurationManager.AppSettings["ConnectionString"];
return new SqlDependencyWebCache(connectionString);
}
}
}
