asp.net-core – 从ActionFilterAttribute设置ViewBag

我正在创建可以由用户设置的自定义颜色的网站(仅在某些页面上).我想在ActionFilterattribute中获取该数据并将其设置在ViewBag中,以便我可以在_Layout.cshtml中获取数据.

这是我的ActionFilterattribute ……

public class PopulateColorOptionsAttribute : ActionFilterattribute
{
    private readonly OptionsDataHelper optionsDataHelper;

    public PopulateOptionsAttribute(OptionsDataHelper optionsDataHelper)
    {
        this.optionsDataHelper = optionsDataHelper;
    }

    public override async Task OnActionExecutionAsync(ActionExecutingContext context,ActionExecutionDelegate next)
    {
        await base.OnActionExecutionAsync(context,next);

        // Get the cemetery data and set it on the view bag.
        var personId = Convert.ToInt32(context.RouteData.Values["personId"]);
        context.Controller.ViewBag.OptionsData = await optionsDataHelper.GetValueAsync(personId,CancellationToken.None);
    }
}

不幸的是,我在ViewBag上收到一条错误,指出：

‘object’ does not contain a deFinition for ‘ViewBag’ and no extension method ‘ViewBag’ accepting a first argument of type ‘object’ Could be found (are you missing a using directive or an assembly reference?) [dnx451]

我很确定我对滤波器没有正确理解,我很欣赏如何实现我想要的指导.

解决方法

ActionExecutingContext.Controller声明为Object类型,因为框架不对哪些类可以作为控制器施加任何限制.

如果您始终创建从基本Controller类继承的控制器,那么您可以在过滤器中使用该假设并将context.Controller用作Controller：

public override async Task OnActionExecutionAsync(ActionExecutingContext context,ActionExecutionDelegate next)
{
    await base.OnActionExecutionAsync(context,next);

    var controller = context.Controller as Controller;
    if (controller == null) return;
    controller.ViewBag.Message = "Foo message";    
}

如果你不能做出这个假设,那么你可以使用类似的方法检查上下文中的结果：

public override async Task OnResultExecutionAsync(ResultExecutingContext context,ResultExecutionDelegate next)
{
    var viewResult = context.Result as ViewResult; //Check also for PartialViewResult and ViewComponentResult
    if (viewResult == null) return;
    dynamic viewBag = new DynamicViewData(() => viewResult.ViewData);
    viewBag.Message = "Foo message";

    await base.OnResultExecutionAsync(context,next);
}