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POASP.NET MVC Post list becomes null under very strange circumstances
 

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  1. POASP.NET MVC Post list becomes null under very strange circumstances
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    <p>So I have a controller like this:</p> <pre><code>public class TestController : Controller { // // GET: /Test/ public ActionResult Index() { return View("Test"); } public ActionResult Post(IList&lt;Test&gt; LanguageStrings, IList&lt;Test&gt; LanguageStringsGroup, IList&lt;string&gt; Deleted, IList&lt;string&gt; DeletedGroup) { if (LanguageStrings == null) { throw new ApplicationException("NULL"); } return View("Test"); } } public class Test { public string Val { get; set; } public string Another { get; set; } } </code></pre> <p>And a view like this:</p> <pre><code>&lt;h2&gt;Test&lt;/h2&gt; @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]") &lt;button&gt;Post&lt;/button&gt; } </code></pre> <p>When I post the form my controller throws the exception because LanguageStrings is null. The strange part I mentioned in the title is that if I add one more record to the list everything works. Like this:</p> <pre><code>&lt;h2&gt;Test&lt;/h2&gt; @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]") &lt;button&gt;Post&lt;/button&gt; } </code></pre> <p>It also works when I remove the "Deleted" list. Like this: </p> <pre><code>&lt;h2&gt;Test&lt;/h2&gt; @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]") &lt;button&gt;Post&lt;/button&gt; } </code></pre> <p>This has something to do with the naming I am using. I have already solved the problem with renaming LanguageStrings to something else. But I would like to understand what is happening here because probably I could learn something from it how MVC maps request body and will be able to avoid similar time consuming problems. Please help me and explain the cause of this.</p>
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