如何将 http 请求转换为正确的对象？

Question

在我的 ASP.Net MVC3 项目中，我创建了一个绑定基本模型的 ModelBinder。在我的视图中，我从继承自基本模型的模型创建一个对象。现在我想知道当我按下提交按钮时，哪个模型是通过 ModelBinder 中的反射创建的，但是如何呢？

ModelBinder:

public class MBTestBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        //need to know which Model was created -> convert into the right object
        //reflection?
    }
}

Models:

[ModelBinder(typeof(MBTestBinder))]
public class MBTest
{
    public string Name { get; set; }
    public MBTest()  {}
}

public class MBAbl : MBTest
{
    public MBAbl()  {}
    public string House { get; set; }
}

View:

@model ModelBinderProject.Models.MBTest

@using (Html.BeginForm("Index", "Home")) {
<fieldset>
    <div class="editor-field">
        @Html.EditorForModel(Model)
    </div>
    <p>
        <input type="submit" value="Create" />
    </p>
</fieldset>

Controller:

public ActionResult Create(MBTest testItem)
{
    //on init get a view from a class that hast inherit the class MBTest
    if (testItem.Name == null ) testItem = new MBAbl();

    return View(testItem);
}

edit:

使用 bindingContext.ValueProvider.GetValue("House") 我可以获取表单的值，但 bindingContext.ModelType 认为我的模型是MBTest

Answer 1

查看 ModelBindingContext 文档。

根据评论进行编辑

public class MBTestBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var result = bindingContext.ValueProvider.GetValue("Name");

        if (result == null || string.IsNullOrEmpty(result.AttemptedValue))
           return new MBAbl();
        else
           return new MBTest();
    }
}

Answer 2

最后，我通过在模型中携带模型名称并在模型绑定器中动态创建正确的模型的解决方法解决了这个问题。
如果您知道更好的解决方案，请告诉我:-)

HomeController:

// CREATE
public ActionResult About(MBTest testItem)
{
    if (testItem == null)
    {
        testItem = new MBAbl();
        testItem.Model = "MBAbl";
    }

    return View(testItem);
}

Models:

public class MBTest
{
    public MBTest()  {}

    [HiddenInput]
    public string Model { get; set; }

    public string Name { get; set; }
}

public class MBAbl : MBTest
{
    public MBAbl()  {}

    public string House { get; set; }
}

public class MBAb2 : MBTest
{
    ...
}

ModelBinder:

public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
    if (controllerContext == null) throw new ArgumentNullException("controllerContext");
    if (bindingContext == null) throw new ArgumentNullException("bindingContext");

    //string 'Model' is needed in the base class
    var modelType = bindingContext.ValueProvider.GetValue("Model");

    if (modelType != null && !string.IsNullOrEmpty(modelType.AttemptedValue))
    {
        string projectName = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name;

        Type classtype = Type.GetType(string.Format("{0}.Models.{1}", projectName, modelType.AttemptedValue));
        PropertyInfo[] properties = classtype.GetProperties();

        var classObject = classtype.GetConstructor(new Type[] { }).Invoke(null);

        foreach (PropertyInfo propertie in properties)
        {
            var value = bindingContext.ValueProvider.GetValue(propertie.Name).AttemptedValue;
            classtype.GetProperty(propertie.Name).SetValue(classObject, value, null);
        }

        return classObject;
    }
    return null;
}

Answer 3

试试这个：

public class ModelBinder : DefaultModelBinder, IModelBinder
{
    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var typeValue = bindingContext.ValueProvider.GetValue("ModelType");
        var type = Type.GetType("Namespace.a.b." + typeValue.AttemptedValue.ToString());

        var model = Activator.CreateInstance(type);

        //Change the model
        bindingContext.ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => model, type);
        bindingContext.ModelMetadata.Model = model;

        //Here, we used the default model binder of the mvc
        return base.BindModel(controllerContext, bindingContext);;
    }
}