Session是互聯網應用中非常重要的玩意兒，對于超過單臺部署的站點集群，都會存在會話共享的需求。在web.config中，微軟提供了sessionstate節點來定義不同的Session狀態存儲方式。本文就自定義模式下的Session狀態存儲驅動提供一些干貨。
首先，想要接管Session狀態存儲，需要了解一些基本的東西。
SessionIDManager
/// <summary> /// 自定義SessionID管理器 /// </summary> public class CustomSessionIDManager : SessionIDManager { /// <summary> /// 創建SessionID /// </summary> /// <param name="context"></param> /// <returns></returns> public override string CreateSessionID(HttpContext context) { return string.Format("{0}.{1}", SessionPRoviderConfigurationSectionHandler.SessionProviderSettings.SessionProfix, base.CreateSessionID(context)); } /// <summary> /// 驗證 /// </summary> /// <param name="id"></param> /// <returns></returns> public override bool Validate(string id) { string prefix = string.Empty; string realId = string.Empty; if (string.IsNullOrEmpty(id) || id.Trim().Length == 0) { return false; } var parsedValues = id.Split('.'); if (parsedValues == null || parsedValues.Length != 2) { return false; } prefix = parsedValues[0]; realId = parsedValues[1]; return base.Validate(realId); } }想要共享Session，肯定就會有SessionID的前綴需求，而SessionIDManager就提供了可自定義的虛方法，這邊以CustomSessionIDManager舉例。CreateSessionID方法提供了創建SessionID的實現，重載該方法，用{0}.{1}的方式提供基于前綴的SessionID生成。而Validate是拆解帶前綴的SessionID來驗證真實的SessionID。
SessionStateStoreProviderBase
/// <summary> /// 自定義Session狀態存儲驅動 /// </summary> public sealed class CustomSessionStateStoreProvider : SessionStateStoreProviderBase { /// <summary> /// 構造函數 /// </summary> public CustomSessionStateStoreProvider() { sessionStateStoreBehavior = SessionProviderBehaviorFactory.CreateSessionStateStoreBehaviorInstance(); } /// <summary> /// Session狀態存儲行為 /// </summary> readonly ISessionStateStoreBehavior sessionStateStoreBehavior; /// <summary> /// 創建新的存儲數據 /// </summary> /// <param name="context"></param> /// <param name="timeout"></param> /// <returns></returns> public override SessionStateStoreData CreateNewStoreData(System.Web.HttpContext context, int timeout) { return new SessionStateStoreData(new SessionStateItemCollection(), SessionStateUtility.GetSessionStaticObjects(context), timeout); } /// <summary> /// 創建未初始化的項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="timeout"></param> public override void CreateUninitializedItem(System.Web.HttpContext context, string id, int timeout) { sessionStateStoreBehavior.CreateUninitializedItem(context, id, timeout); } /// <summary> /// 獲取項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="locked"></param> /// <param name="lockAge"></param> /// <param name="lockId"></param> /// <param name="actions"></param> /// <returns></returns> public override SessionStateStoreData GetItem(System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions) { return sessionStateStoreBehavior.GetItem(false, context, id, out locked, out lockAge, out lockId, out actions); } /// <summary> /// 獨占獲取項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="locked"></param> /// <param name="lockAge"></param> /// <param name="lockId"></param> /// <param name="actions"></param> /// <returns></returns> public override SessionStateStoreData GetItemExclusive(System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions) { return sessionStateStoreBehavior.GetItem(true, context, id, out locked, out lockAge, out lockId, out actions); } /// <summary> /// 獨占釋放項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="lockId"></param> public override void ReleaseItemExclusive(System.Web.HttpContext context, string id, object lockId) { sessionStateStoreBehavior.ReleaseItem(context, id, lockId); } /// <summary> /// 移除項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="lockId"></param> /// <param name="item"></param> public override void RemoveItem(System.Web.HttpContext context, string id, object lockId, SessionStateStoreData item) { sessionStateStoreBehavior.RemoveItem(context, id, lockId); } /// <summary> /// 重設項的超時時間 /// </summary> /// <param name="context"></param> /// <param name="id"></param> public override void ResetItemTimeout(System.Web.HttpContext context, string id) { sessionStateStoreBehavior.ResetItemTimeout(context, id); } /// <summary> /// 獨占設置并釋放項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="item"></param> /// <param name="lockId"></param> /// <param name="newItem"></param> public override void SetAndReleaseItemExclusive(System.Web.HttpContext context, string id, SessionStateStoreData item, object lockId, bool newItem) { sessionStateStoreBehavior.SetAndReleaseItem(context, id, item, lockId, newItem); } /// <summary> /// 回收 /// </summary> public override void Dispose() { } /// <summary> /// 結束請求 /// </summary> /// <param name="context"></param> public override void EndRequest(System.Web.HttpContext context) { } /// <summary> /// 初始化請求 /// </summary> /// <param name="context"></param> public override void InitializeRequest(System.Web.HttpContext context) { } /// <summary> /// 設置項過期回掉 /// </summary> /// <param name="expireCallback"></param> /// <returns></returns> public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback) { return false; } }SessionStateStoreProviderBase是提供Session狀態存儲驅動的基類。從基類分析，想要靈活擴展，核心就是對Session存儲的那些方法實現進行抽象，讓驅動在執行方法的時候不關心實現由誰來提供。因此，寫一個SessionStateStoreBehavior接口，在CustomSessionStateStoreProvider的構造函數中，通過工廠在運行時得到實例。
SessionStateStoreBehavior
/// <summary> /// Session狀態存儲行為接口 /// </summary> public interface ISessionStateStoreBehavior { /// <summary> /// 創建未初始化的項 /// </summary> /// <param name="context"></param> /// <param name="id"></param> /// <param name="timeout"></param> void CreateUninitializedItem(System.Web.HttpContext context, string id, int t
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