asp.net-mvc – 通过F#代码迭代插入ASP.NET MVC4页面的ViewData

发布时间：2020-12-16 06:27:47 所属栏目：asp.Net 来源：网络整理

导读：叫我疯了,但我正在用F#开发一个ASP.NET MVC4站点.这是我的第一个障碍;在控制器中我提交字典,这样： [HandleError]type FooController() = inherit Controller() member this.Index () = this.ViewData.Add("Foo","Bar") this.ViewData.Add("Baz",dict [ (0,0

叫我疯了,但我正在用F#开发一个ASP.NET MVC4站点.这是我的第一个障碍;在控制器中我提交字典,这样：

[<HandleError>]
type FooController() =
    inherit Controller()
    member this.Index () =
        this.ViewData.Add("Foo","Bar")
        this.ViewData.Add("Baz",dict [ (0,0); (1,3); (2,2); ] )
        this.View() :> ActionResult

现在我想迭代Razor模板中的值,该怎么做？我试过这个：

@foreach (var time in @ViewBag.Baz.Keys)
{
    <hr /><p>Time is @time,and value is @ViewBag.Baz[time]</p>
}

但它抛出了这个错误：

Line 119:                    Total: <span class="highlight">6449</span> kW/h.
Line 120:                </p>
Line 121:                @foreach (var time in (@ViewBag.Baz).Keys)
Line 122:                {
Line 123:                    <hr /><p>Time is @time,and value is @ViewBag.Baz[time]</p>

[RuntimeBinderException: 'object' does not contain a definition for 'Keys']
   CallSite.Target(Closure,CallSite,Object ) +280
   System.Dynamic.UpdateDelegates.UpdateAndExecute1(CallSite site,T0 arg0) +924
   ASP._Page_Views_lobby_Index_cshtml.Execute() in c:Usersknoctedocumentsvisual studio 2012projectsfsolarconclavesolarwebconclavesolarwebwebapiViewsLobbyIndex.cshtml:121
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +280
   System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +126
   System.Web.WebPages.StartPage.ExecutePageHierarchy() +143
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext,TextWriter writer,WebPageRenderingBase startPage) +181
   System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +378
   System.Web.Mvc.<>c__DisplayClass1a.<InvokeActionResultWithFilters>b__17() +33
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter,ResultExecutingContext preContext,Func`1 continuation) +853420
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext,IList`1 filters,ActionResult actionResult) +265
   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +837892
   System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +28
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +15
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +65
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +15
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +51
   System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +15
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +51
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +606
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step,Boolean& completedSynchronously) +288

解决方法

所以你遇到的问题是动态关键字和 explicit interface implementations的已知限制.不幸的是,地图也会遇到这个问题.如果你真的想要使用这样的ViewBag,你可以使用实际的Dictionary< int,int>.

最终,你应该发挥F#的优势,即静态打字和低礼式类型创作.在F#代码中创建轻量级类型,并在视图中使用@model keyword.

（编辑：李大同）

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