c# - 如何访问 ExecuteResultAsync 中的 ViewDataDictionary？

Question

介绍

我正在尝试Action - ViewResult使用扩展方法进行装饰。目标是能够ViewData在 Decorator 的使用范围内，在Controller. 但是，我只能在TempData我想访问ViewDatamethod 内部时访问ExecuteResultAsync。

问题

如何在访问 ActionContext 的过程中从 ExecuteResultAsync 访问 ViewData？这完全可能是以下情况吗？

设想

因此，不要编写以下内容：

public async Task<IActionResult> ChangePassword()
{
    ViewData["Title"] = "Change Password";
    return PartialView("_ChangePasswordPartial",...);
}

我试图让它像这样工作：

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

扩展方法：

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

装饰师：

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);
      }
}

Answer 1

因为ViewData，你无法解决它context.HttpContext.RequestServices.GetService。

/// <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

如上所述，您只能访问ViewDatainController和OnActionExecuting(ActionExecutingContext)。您无法通过已解决的服务访问它。

您可以尝试ViewData通过反映IActionResult.

尝试

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);
    }
}