C# 如何在ExecuteSultAsync中访问ViewDataDictionary？ 简介

我试图在扩展方法的使用中装饰

Action-ViewResult

。目标是能够在Decorator的使用范围内，在

控制器

之外设置

视图数据

。但是，我只能访问

TempData

，而我想访问

ViewData

方法

executesultasync

的内部

问题 如何在访问ActionContext的过程中从ExecuteSultAsync访问ViewData？这是下面的吗 有可能吗

脚本 所以不要写以下内容：

装饰师：

public async Task<IActionResult> ChangePassword()
{
    return PartialView("_ChangePasswordPartial",...).WithTitle("Change Password");
}

public static IActionResult WithTitle(this IActionResult action, string modalTitle)
{
    return new ModalTitleDecorator(action,modalTitle);
}

public class ModalTitleDecorator : ActionResult
{
     private readonly IActionResult _actionResult;
     private readonly string _modalTitle;

     public ModalTitleDecorator(IActionResult action, string modalTitle)
     {
         _actionResult = action;
         _modalTitle = modalTitle;
     }

      public override async Task ExecuteResultAsync(ActionContext context)
      {

          var tempData = context.HttpContext.RequestServices.GetService<ITempDataDictionaryFactory>()
                   .GetTempData(context.HttpContext);

         //always null...I assume that ViewData is not available according to HttpContext. 
         //TempData is available probably according to passing into next request.
         var viewData = context.HttpContext.RequestServices.GetService<ViewDataDictionary>();

         //something like this would be great
         ViewData["Title"] = _modalTitle;

         await _actionResult.ExecuteResultAsync(context);
      }
}

公共类ModalTitleDecorator:ActionResult
{
私有只读IActionResult\u actionResult；
私有只读字符串_modaltle；
公共ModalTitleDecorator（IActionResult操作，字符串modalTitle）
{
_行动结果=行动；
_modalTitle=modalTitle；
}
公共重写异步任务ExecuteSultAsync（ActionContext上下文）
{
var tempData=context.HttpContext.RequestServices.GetService（）
.GetTempData（context.HttpContext）；
//始终为空…我假设ViewData根据HttpContext不可用。
//TempData可能根据传递到下一个请求而可用。
var viewData=context.HttpContext.RequestServices.GetService（）；
//像这样的东西太好了
ViewData[“标题”]=\u MODALITLE；
wait_actionResult.executeSultAsync（上下文）；
}
}

对于

视图数据

，您无法通过

context.HttpContext.RequestServices.GetService

解析它

/// <summary>
/// Gets or sets <see cref="ViewDataDictionary"/> used by <see cref="ViewResult"/> and <see cref="ViewBag"/>.
/// </summary>
/// <remarks>
/// By default, this property is intiailized when <see cref="Controllers.IControllerActivator"/> activates
/// controllers.
/// <para>
/// This property can be accessed after the controller has been activated, for example, in a controller action
/// or by overriding <see cref="OnActionExecuting(ActionExecutingContext)"/>.
/// </para>
/// <para>
/// This property can be also accessed from within a unit test where it is initialized with
/// <see cref="EmptyModelMetadataProvider"/>.
/// </para>
/// </remarks>
[ViewDataDictionary]
public ViewDataDictionary ViewData

---

很好，很好用。然而，反射的表现是什么？开销是不是很小，我不必处理？

/// <summary>
/// Gets or sets <see cref="ViewDataDictionary"/> used by <see cref="ViewResult"/> and <see cref="ViewBag"/>.
/// </summary>
/// <remarks>
/// By default, this property is intiailized when <see cref="Controllers.IControllerActivator"/> activates
/// controllers.
/// <para>
/// This property can be accessed after the controller has been activated, for example, in a controller action
/// or by overriding <see cref="OnActionExecuting(ActionExecutingContext)"/>.
/// </para>
/// <para>
/// This property can be also accessed from within a unit test where it is initialized with
/// <see cref="EmptyModelMetadataProvider"/>.
/// </para>
/// </remarks>
[ViewDataDictionary]
public ViewDataDictionary ViewData

public static class ActionResultExtension
{
    public static IActionResult WithTitle(this IActionResult action, string modalTitle)
    {
        return new ModalTitleDecorator(action, modalTitle);
    }
}

public class ModalTitleDecorator : PartialViewResult
{
    private readonly IActionResult _actionResult;
    private readonly string _modalTitle;

    public ModalTitleDecorator(IActionResult action, string modalTitle)
    {
        _actionResult = action;
        _modalTitle = modalTitle;
    }

    public override async Task ExecuteResultAsync(ActionContext context)
    {
        ViewDataDictionary viewData = _actionResult
                                    .GetType()
                                    .GetProperty("ViewData")
                                    .GetValue(_actionResult) as ViewDataDictionary;
        if (viewData != null)
        {
            viewData["Title"] = _modalTitle;
        }
        await _actionResult.ExecuteResultAsync(context);
    }
}