在非常奇怪的情况下,ASP.NET MVC Post列表变为null

Question

所以我有一个像这样的控制器:

public class TestController : Controller
    {
        //
        // GET: /Test/

        public ActionResult Index()
        {
            return View("Test");
        }

        public ActionResult Post(IList<Test> LanguageStrings, IList<Test> LanguageStringsGroup, IList<string> Deleted, IList<string> DeletedGroup)
        {
            if (LanguageStrings == null)
            {
                throw new ApplicationException("NULL");
            }


            return View("Test");
        }

    }

    public class Test
    {
        public string Val { get; set; }
        public string Another { get; set; }
    }

这样的观点:

<h2>Test</h2>

@using (Html.BeginForm("Post", "Test"))
{
    @Html.Hidden("LanguageStrings[0].Val", "test1")
    @Html.Hidden("LanguageStrings[0].Another")
    @Html.Hidden("LanguageStrings[1].Val", "test2")
    @Html.Hidden("LanguageStrings[1].Another")

    @Html.Hidden("LanguageStringsGroup[0].Val", "test4")

    @Html.Hidden("Deleted[0]")
    @Html.Hidden("Deleted[1]")
    @Html.Hidden("Deleted[2]")

    @Html.Hidden("DeletedGroup[0]")

    <button>Post</button>
}

当我发布表单时,我的控制器会抛出异常,因为LanguageStrings为null.我在标题中提到的一个奇怪的部分是,如果我在列表中再添加一条记录,一切正常.像这样:

<h2>Test</h2>

@using (Html.BeginForm("Post", "Test"))
{
    @Html.Hidden("LanguageStrings[0].Val", "test1")
    @Html.Hidden("LanguageStrings[0].Another")
    @Html.Hidden("LanguageStrings[1].Val", "test2")
    @Html.Hidden("LanguageStrings[1].Another")
    @Html.Hidden("LanguageStrings[2].Val", "test3")
    @Html.Hidden("LanguageStrings[2].Another")

    @Html.Hidden("LanguageStringsGroup[0].Val", "test4")

    @Html.Hidden("Deleted[0]")
    @Html.Hidden("Deleted[1]")
    @Html.Hidden("Deleted[2]")

    @Html.Hidden("DeletedGroup[0]")

    <button>Post</button>
}

当我删除"已删除"列表时,它也有效.像这样:

<h2>Test</h2>

@using (Html.BeginForm("Post", "Test"))
{
    @Html.Hidden("LanguageStrings[0].Val", "test1")
    @Html.Hidden("LanguageStrings[0].Another")
    @Html.Hidden("LanguageStrings[1].Val", "test2")
    @Html.Hidden("LanguageStrings[1].Another")

    @Html.Hidden("LanguageStringsGroup[0].Val", "test4")

    @Html.Hidden("DeletedGroup[0]")

    <button>Post</button>
}

这与我正在使用的命名有关.我已经解决了将LanguageStrings重命名为其他问题的问题.但是我想了解这里发生了什么,因为我可以从中学到一些东西,MVC如何映射请求体,并且能够避免类似的耗时问题.请帮助我解释原因.

Answer 1

您在MVC 4的PrefixContainer中发现了一个已在MVC 5中修复的错误.

这是修复版本,其中包含有关该错误的评论:

internal bool ContainsPrefix(string prefix)
{
    if (prefix == null)
    {
        throw new ArgumentNullException("prefix");
    }

    if (prefix.Length == 0)
    {
        return _sortedValues.Length > 0; // only match empty string when we have some value
    }

    PrefixComparer prefixComparer = new PrefixComparer(prefix);
    bool containsPrefix = Array.BinarySearch(_sortedValues, prefix, prefixComparer) > -1;
    if (!containsPrefix)
    {
        // If there's something in the search boundary that starts with the same name
        // as the collection prefix that we're trying to find, the binary search would actually fail.
        // For example, let's say we have foo.a, foo.bE and foo.b[0]. Calling Array.BinarySearch
        // will fail to find foo.b because it will land on foo.bE, then look at foo.a and finally
        // failing to find the prefix which is actually present in the container (foo.b[0]).
        // Here we're doing another pass looking specifically for collection prefix.
        containsPrefix = Array.BinarySearch(_sortedValues, prefix + "[", prefixComparer) > -1;
    }
    return containsPrefix;
}