我为此设计了一个可能的解决方案原型，因为这似乎是一个有趣的问题。我希望它对你有用。
型号
首先，模型。我决定创建两个“小部件”，一个用于新闻，一个用于时钟。
public class NewsModel
{
public string[] Headlines { get; set; }
public NewsModel(params string[] headlines)
{
Headlines = headlines;
}
}
public class ClockModel
{
public DateTime Now { get; set; }
public ClockModel(DateTime now)
{
Now = now;
}
}
控制器
我的控制器对视图一无所知。它所做的是返回单个模型，但该模型能够根据视图的要求动态获取正确的模型。
public ActionResult Show(string widgetName)
{
var selector = new ModelSelector();
selector.WhenRendering<ClockModel>(() => new ClockModel(DateTime.Now));
selector.WhenRendering<NewsModel>(() => new NewsModel("Headline 1", "Headline 2", "Headline 3"));
return PartialView(widgetName, selector);
}
使用委托以便仅在实际使用时创建/获取正确的模型。
模型选择器
控制器使用的 ModelSelector 非常简单 - 它只保留一袋代表来创建每种模型类型：
public class ModelSelector
{
private readonly Dictionary<Type, Func<object>> modelLookup = new Dictionary<Type, Func<object>>();
public void WhenRendering<T>(Func<object> getter)
{
modelLookup.Add(typeof(T), getter);
}
public object GetModel(Type modelType)
{
if (!modelLookup.ContainsKey(modelType))
{
throw new KeyNotFoundException(string.Format("A provider for the model type '{0}' was not provided", modelType.FullName));
}
return modelLookup[modelType]();
}
}
视图 - 简单的解决方案
现在，实现视图的最简单方法是：
@model MvcApplication2.ModelSelector
@using MvcApplication2.Models
@{
var clock = (ClockModel) Model.GetModel(typeof (ClockModel));
}
<h2>The time is: @clock.Now</h2>
你可以在这里结束并使用这种方法。
观点 - 更好的解决方案
这太丑了。我希望我的视图看起来像这样：
@model MvcApplication2.Models.ClockModel
<h2>Clock</h2>
@Model.Now
和
@model MvcApplication2.Models.NewsModel
<h2>News Widget</h2>
@foreach (var headline in Model.Headlines)
{
<h3>@headline</h3>
}
为了完成这项工作，我必须创建一个自定义视图引擎。
自定义视图引擎
编译 Razor 视图时，它会继承 ViewPage<T>，其中 T 是 @model。所以我们可以使用反射来确定视图想要什么类型，然后选择它。
public class ModelSelectorEnabledRazorViewEngine : RazorViewEngine
{
protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
{
var result = base.CreateView(controllerContext, viewPath, masterPath);
if (result == null)
return null;
return new CustomRazorView((RazorView) result);
}
protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
{
var result = base.CreatePartialView(controllerContext, partialPath);
if (result == null)
return null;
return new CustomRazorView((RazorView)result);
}
public class CustomRazorView : IView
{
private readonly RazorView view;
public CustomRazorView(RazorView view)
{
this.view = view;
}
public void Render(ViewContext viewContext, TextWriter writer)
{
var modelSelector = viewContext.ViewData.Model as ModelSelector;
if (modelSelector == null)
{
// This is not a widget, so fall back to stock-standard MVC/Razor rendering
view.Render(viewContext, writer);
return;
}
// We need to work out what @model is on the view, so that we can pass the correct model to it.
// We can do this by using reflection over the compiled views, since Razor views implement a
// ViewPage<T>, where T is the @model value.
var compiledViewType = BuildManager.GetCompiledType(view.ViewPath);
var baseType = compiledViewType.BaseType;
if (baseType == null || !baseType.IsGenericType)
{
throw new Exception(string.Format("When the view '{0}' was compiled, the resulting type was '{1}', with base type '{2}'. I expected a base type with a single generic argument; I don't know how to handle this type.", view.ViewPath, compiledViewType, baseType));
}
// This will be the value of @model
var modelType = baseType.GetGenericArguments()[0];
if (modelType == typeof(object))
{
// When no @model is set, the result is a ViewPage<object>
throw new Exception(string.Format("The view '{0}' needs to include the @model directive to specify the model type. Did you forget to include an @model line?", view.ViewPath));
}
var model = modelSelector.GetModel(modelType);
// Switch the current model from the ModelSelector to the value of @model
viewContext.ViewData.Model = model;
view.Render(viewContext, writer);
}
}
}
通过将其放入 Global.asax.cs 来注册视图引擎：
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(new ModelSelectorEnabledRazorViewEngine());
渲染
我的主页视图包括以下几行来测试它：
@Html.Action("Show", "Widget", new { widgetName = "Clock" })
@Html.Action("Show", "Widget", new { widgetName = "News" })