多态视图模型收集和呈现在MVC局部视图 [英] Polymorphic ViewModel collection and rendering in MVC partial Views

问题描述

我在与我的MVC应用程序中的ViewModels的多态集合的问题。我通过一个Web服务调用收到此，我需要通过他们迭代，并给他们自己的局部视图，基于对象的类型。

I'm having a problem with a polymorphic collection of ViewModels in my MVC application. I received this via a web service call and i need to iterate through them and give them their own partial view, based on the object type.

public abstract class ProvinceViewModel
{
    public string Code { get; set; }
}

public sealed class OntarioViewModel : ProvinceViewModel { }

public sealed class QuebecViewModel : ProvinceViewModel {}

在我看来，我试图通过它们进行迭代并分配的局部视图。我也做了很多类型转换的位置，使其工作。如果我尝试和移动这一个控制器动作，并通过在抽象类型，我会得到，我们不能创建抽象类的实例错误。

In my view i am trying to iterate through them and assign a partial view. I have to do a lot of type casting here to make it work. If I try and move this to a controller action and pass in the abstract type, i will get an error that we cannot create an instance of abstract class.

ICollection<ProvinceViewModel>  ProvinceList; // collection receive via service

@for (int i = 0, c = ProvinceList.Count; i < c; i++)
{
    var currentProvince = this.Model.ElementAt(i);
    @switch (additionalRegistry.Code)
    {
        case "QC":
            @Html.Partial("AlbertaDetail", (QuebecViewModel)currentProvince)
            break;                              
        case "ON":
            @Html.Partial("OntarioDetail", (OntarioViewModel)currentProvince)
            break;
        default:
            @Html.Partial("ProvinceDetail", ProvinceViewModel)
            break;
    }
}

我强类型视图，这样我可以访问不同的属性。

I have strongly type View, so that i can access the different properties.

我将如何去在一个更优雅的方式解决这个？我需要创建一个新的代理基类的抽象类来创建它的一个实例，更容易？

How would i go about solving this in a more elegant way? Would I need to create a new surrogate base class for the abstract class to create a instance of it easier?

推荐答案

一旦在过去遇到了同样的问题，我创建了以下解决方案：

Upon encountering the same problem in the past, I have created the following solution:

首先，装点您的（混凝土）视图模型使用表示要使用的视图名称 ExportMetadata 属性。例如：

First, decorate your (concrete) view-model with ExportMetadata attribute that denotes the view name to be used. For example:

[ExportMetadata("View", "Ontario")]
public sealed class OntarioViewModel : ProvinceViewModel { }

[ExportMetadata("View", "Quebec")]
public sealed class QuebecViewModel : ProvinceViewModel {}

那么你的的HtmlHelper 具有以下部分方法扩展：

public static MvcHtmlString Partial<T>(this HtmlHelper htmlHelper, T model, string prefix = null)
{
    var modelType = typeof (T);
    var partialAttr = modelType.GetCustomAttributes<ExportMetadataAttribute>().SingleOrDefault(x => x.Name == "View");

    if (partialAttr == null)
        throw new Exception(modelType.Name + " doesn't define any view to be used");

    var partialName = (prefix ?? String.Empty) + partialAttr.Value;

    return htmlHelper.Partial(partialName, model, htmlHelper.ViewData);
}

然后使用它：

@Html.Partial(currentProvince);

和在情况下，你的谐音存在于某些子目录：

And in case your partials reside in some sub-directory:

@Html.Partial(currentProvince, "Partials/")

（如果您需要帮助注册自定义HTML辅助见 http://stackoverflow.com/a/5052790 ）

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