asp.net-mvc – MVC模型绑定：为什么我不能绑定到迭代器属性？

示例型号：

namespace ModelBinderTest
{
    using System.Collections.Generic;
    public class MyModel
    {
        private List<string> fooBacking = new List<string>();
        public IEnumerable<string> Foo
        {
            get
            {
                foreach (var o in fooBacking)
                {
                    yield return o; // <-- ITERATOR BREAKS MODEL BINDING
                }
            }
            set { fooBacking = new List<string>(value); }
        }

        private List<string> barBacking = new List<string>();
        public IEnumerable<string> Bar
        {
            get
            {
                // Returning any non-iterator IEnumerable works here. Eg:
                return new List<string>(barBacking);
            }
            set { barBacking = new List<string>(value); }
        }
    }
}

失败的例子1：

namespace ModelBinderTest
{
    using System;
    using System.Linq;
    using System.Web.Mvc;
    using Microsoft.VisualStudio.TestTools.UnitTesting;

    [TestClass]
    [CLSCompliant(false)]
    public class DefaultModelBinderTestIterator
    {
        [TestMethod]
        public void BindsIterator()
        {
            // Arrange
            var model = new MyModel();

            ModelBindingContext bindingContext = new ModelBindingContext()
            {
                FallbackToEmptyPrefix = true,ModelMetadata = ModelMetadataProviders
                                  .Current
                                  .GetMetadataForType(null,model.GetType()),ModelName = "",ValueProvider = new NameValueCollectionValueProvider(
                    new System.Collections.Specialized.NameValueCollection()
                        {
                            { "Foo[0]","foo" },{ "Bar[0]","bar" },},System.Globalization.CultureInfo.InvariantCulture
                )
            };

            DefaultModelBinder binder = new DefaultModelBinder();

            // Act
            MyModel updatedModel = (MyModel)binder.BindModel(
                                     new ControllerContext(),bindingContext);

            // Assert
            Assert.AreEqual(1,updatedModel.Bar.Count(),"Bar property should have been updated");
            Assert.AreEqual("bar",updatedModel.Bar.ElementAtOrDefault(0),"Bar's first element should have been set");

            Assert.AreEqual(1,updatedModel.Foo.Count(),"Foo property should have been updated");
            Assert.AreEqual("foo",updatedModel.Foo.ElementAtOrDefault(0),"Foo's first element should have been set");
        }

    }
}

上面的单元测试会将我模型的Bar属性更新为[“bar”]没问题(在集合键中有或没有方括号),但是无法将任何内容绑定到Foo属性.

有没有人知道(在低级别)为什么实现IEnumerable属性作为迭代器会导致模型绑定失败？

我对workarounds2并不感兴趣,而是对一些分析感兴趣,因为我已经用尽了我对框架这方面的了解;)

1：单元测试是分离SO问题的最简单方法,而不是通过整个MVC应用程序示例.

2：例如,我知道如果我从输入中删除方括号并为所有值重用相同的“Foo”键,则模型绑定将起作用.然而,真正的失败案例需要方括号,因为集合中的每个项目都是具有自己的子属性的复杂类型.或者另一种解决方法：添加非迭代器IEnumerable< T>操作的参数,并将其直接分配给操作中的属性.啊.