ASP.NET MVC ActionResult 本質解析第四篇：HttpStatusCodeResult 與重導向結果

HttpStatusCodeResult：自訂 HTTP 狀態碼回應

public class HttpStatusCodeResult : ActionResult
{
    public HttpStatusCodeResult(int statusCode);
    public HttpStatusCodeResult(HttpStatusCode statusCode);
    public HttpStatusCodeResult(int statusCode, string statusDescription);
    public HttpStatusCodeResult(HttpStatusCode statusCode, string statusDescription);
    
    public override void ExecuteResult(ControllerContext context)
    {
        context.HttpContext.Response.StatusCode = StatusCode;
        if (StatusDescription != null)
            context.HttpContext.Response.StatusDescription = StatusDescription;
    }
    public int StatusCode { get; }
    public string StatusDescription { get; }
}

注意事項

• Visual Studio Development Server (Cassini) 忽略 StatusDescription，需 IIS 才生效。
• 常用狀態碼：404 Not Found、401 Unauthorized、500 Internal Server Error。

兩大衍生類別

• HttpNotFoundResult：new HttpStatusCodeResult(404)，Controller 提供 HttpNotFound() 便利方法。
• HttpUnauthorizedResult：new HttpStatusCodeResult(401)，AuthorizeAttribute 驗證失敗時回傳。

RedirectResult：URL 重導向

public class RedirectResult : ActionResult
{
    public RedirectResult(string url);
    public RedirectResult(string url, bool permanent);
    
    public override void ExecuteResult(ControllerContext context)
    {
        string url = UrlHelper.GenerateContentUrl(Url, context.HttpContext);
        if (Permanent)
            context.HttpContext.Response.RedirectPermanent(url, false); // 301
        else
            context.HttpContext.Response.Redirect(url, false); // 302
    }
    public bool Permanent { get; }
    public string Url { get; }
}

暫時 vs 永久重導向

Controller 提供 Redirect(url) (302) 與 RedirectPermanent(url) (301) 便利方法。

RedirectToRouteResult：路由導向重導向

public class RedirectToRouteResult : ActionResult
{
    public RedirectToRouteResult(RouteValueDictionary routeValues);
    public RedirectToRouteResult(string routeName, RouteValueDictionary routeValues);
    public RedirectToRouteResult(RouteValueDictionary routeValues, bool permanent);
    public RedirectToRouteResult(string routeName, RouteValueDictionary routeValues, bool permanent);
    
    public override void ExecuteResult(ControllerContext context)
    {
        var url = UrlHelper.GenerateUrl(RouteName, null, null, RouteValues, RouteTable.Routes, context.RequestContext, true);
        if (Permanent) context.HttpContext.Response.RedirectPermanent(url, false);
        else context.HttpContext.Response.Redirect(url, false);
    }
    public RouteValueDictionary RouteValues { get; }
    public string RouteName { get; }
    public bool Permanent { get; }
}

優勢

• 不硬編碼 URL，透過路由表產生，支援區域、參數自動編碼。
• Controller 提供 RedirectToAction(action, controller)、RedirectToRoute(routeValues) 等多載。

總結

HttpStatusCodeResult 為低層級 HTTP 狀態控制，RedirectResult 與 RedirectToRouteResult 封裝 301/302 重導向語意。實務上優先使用 Controller 便利方法 (HttpNotFound、RedirectToAction 等) 而非直接實例化 Result 類別。