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如何访问ExecuteResultAsync内的ViewDataDictionary?

asp.net-core-2.0 asp.net-core-mvc asp.net-core c#

Arsiwaldi · 技术社区 · 5 年前

简介

我想装饰一下 Action - ViewResult 使用扩展方法。目标是能够设定的 ViewData 在装饰师的使用范围内,在 Controller . 但是,我只能访问 TempData 但是我想进入 可视数据 方法内部 ExecuteResultAsync .

问题

如何在访问ActionContext的过程中从ExecuteResultAsync访问viewData?这是下列吗可能的情况?

脚本

因此,不要写以下内容:

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

我想让它像这样工作:

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);
}

装饰者:

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);
      }
}

1 回复 | 直到 5 年前

Edward 5 年前

为了 ViewData ,无法通过解决 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 可视数据 在里面 Controller 和 OnActionExecuting(ActionExecutingContext) . 您无法通过解析的服务访问它。

你可以试着进入 可视数据 通过反射 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);
    }
}