ASP.NET MVC 核心教程（六）：Filter 過濾器實作權限驗證與快取策略

適用情境

• 登入/權限驗證
• 輸出快取決策
• 防盜連結、防爬蟲
• 本地化/國際化設定
• 動態 Action 實作

自訂 Filter 範例

public class TestFilter : ActionFilterAttribute {
    public override void OnActionExecuting(ActionExecutingContext filterContext) {
        filterContext.HttpContext.Session["temp"] += "OnActionExecuting<br/>";
    }
    public override void OnActionExecuted(ActionExecutedContext filterContext) { ... }
    public override void OnResultExecuting(ResultExecutingContext filterContext) { ... }
    public override void OnResultExecuted(ResultExecutedContext filterContext) { ... }
}

[TestFilter]
public ActionResult filteraction() { return View(); }

四個切入點執行順序：OnActionExecuting → Action → OnActionExecuted → OnResultExecuting → View → OnResultExecuted。