Question

我正在尝试在没有给出视图模型时（当它们为空时）实现视图模型的自动实例化。

控制器操作

public ActionResult SomeAction()
{
    return View("~/.../SomeView.cshtml"); //No model is given
}

SomeView.cshtml

@model Models.SomeModel //According to this type...
<h2>@Model.Title</h2>
//...auto instantiate @Model when it is null

我试图覆盖RazorViewEngine，但似乎（我可能是错的）在ViewEngine时我无法访问模型类型，它总是为null，即使它被提供。我应该能够学习null模型的类型，因为我们正在尝试实例化它，所以应该有另一个元数据，我们可以获取View的模型类型。

我尝试过扩展DefaultModelBinder，但它似乎只是用于绑定来自Http请求的模型，它不会触发创建手动视图。

我没有想法。我希望这样做是可行的。

Answer 1

在BorysG的帮助下，我们已经解决了它，我也改进了它以使用Partials。

讨论：http://forums.asp.net/t/1924332.aspx/1?ASP+NET+MVC+Automatic+Model+Instantiation+if+Model+is+not+provided

此处复制代码：

public class CustomViewEngine : RazorViewEngine
{
    protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
    {
        var view = base.CreatePartialView(controllerContext, partialPath);

        return new ViewWrapper(view);
    }

    protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
    {
        var view = base.CreateView(controllerContext, viewPath, masterPath);

        return new ViewWrapper(view);
    }
}

public class ViewWrapper : IView
{
    protected IView View;

    public ViewWrapper(IView view)
    {
        View = view;
    }

    public void Render(ViewContext viewContext, TextWriter writer)
    {
        //Type modelType = BuildManager.GetCompiledType(razorView.ViewPath);
        var razorView = View as RazorView;

        if (razorView != null)
        {
            //if we could not get the model object - try to get it from what is declared in view
            var compiledViewType = BuildManager.GetCompiledType(razorView.ViewPath);

            var model = viewContext.ViewData.Model;

            Type baseType = compiledViewType.BaseType;
            //model is passed as generic parameter, like this MyView1 : WebViewPage<MyModel1>
            if (baseType != null && baseType.IsGenericType)
            {
                //and here the trick begins - extract type of model from generic arguments
                var modelType = baseType.GetGenericArguments()[0]; //the same as typeof(MyModel1)

                // ReSharper disable UseMethodIsInstanceOfType
                //If model is null, or model is not type of the given model (for partials)
                if (model == null || !modelType.IsAssignableFrom(model.GetType()))
                // ReSharper restore UseMethodIsInstanceOfType
                {
                    //Set @model and render the view
                    viewContext.ViewData.Model = Activator.CreateInstance(modelType);
                }
            }
        }

        View.Render(viewContext, writer);
    }
}

还有Application_Start（）中的Global.asax.cs。

//remove default Razor and WebForm view engines
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(new CustomViewEngine());

如果未提供Model，则为ASP.NET MVC自动模型实例化

1 个答案: