当我期望值时，IEnumerable为null [英] IEnumerable is null when I expect values

问题描述

我正在使用

I am using the approach in this article to return a list of objects that are posted to my action. My method looks like:

    //
    // POST: /LeaveRequest/Create
    [Authorize, HttpPost]
    public ActionResult Create(LeaveRequest leaveRequest, IEnumerable<DayRequested> requestedDays)
    {
        return RedirectToAction("Index", lrRepository.GetLeaveRequests(472940821));
    }

leaveRequest具有我期望的数据. requestedDays包含我期望的行数，但是所有行在每个字段中都包含null.关于我可能会缺少的任何想法吗?

leaveRequest has the data that I expect. requestedDays contains the number of rows I expect, but all of the rows contain null in each field. Any ideas of what I may be missing?

这是查看代码:

Create.aspx

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<EmployeePayroll.ViewModels.LeaveRequestViewModel>" %>
<%@ Import Namespace="EmployeePayroll.Helpers"%>
<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">Create New Leave Request</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <h2>Create New Leave Request</h2>
    <div><%= Html.ActionLink("Back to List", "Index") %></div>
    <%= Html.Partial("RequestEditor", Model) %>
    <div><%= Html.ActionLink("Back to List", "Index") %></div>
</asp:Content>

RequestEditor.ascx

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<EmployeePayroll.ViewModels.LeaveRequestViewModel>" %>
<% using (Html.BeginForm()) {%>
    <%= Html.ValidationSummary(true) %>
    <fieldset>
        <legend>Request Details</legend>
        <table>
             <tbody id="editorRows">
                <tr><th>Date</th><th>Time</th><th>Hours</th><th>Request Type</th><th></th></tr>
                <% foreach (var item in Model.DaysRequested)
                    Html.RenderPartial("RequestedDayRow", new EmployeePayroll.ViewModels.LeaveRequestRow(item, Model.LeaveRequestType)); %>
            </tbody>
        </table>
        <p><%= Html.ActionLink("Add Day", "BlankRequestedDayRow", null, new { id = "addItem" })%></p>

        <p>Type your time to sign your request.</p>
        <p><%= Html.LabelFor(model => model.LeaveRequest.EmployeeSignature) %>: <%= Html.TextBoxFor(model => model.LeaveRequest.EmployeeSignature, new { Class="required" })%></p>
        <p><%= Html.LabelFor(model => model.LeaveRequest.EmployeeComment) %>: <%= Html.TextBoxFor(model => model.LeaveRequest.EmployeeComment) %></p>
        <p><input type="submit" value="Submit Request" /></p>
    </fieldset>
<% } %>

RequestedDayRow.ascx

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<EmployeePayroll.ViewModels.LeaveRequestRow>" %>
<%@ Import Namespace="EmployeePayroll.Helpers"%>

<tr class="editorRow">
    <% using (Html.BeginCollectionItem("requestedDays"))
   { %>
        <td><%= Html.TextBoxFor(model => model.DayRequested.DateOfLeave, new { Class = "datepicker", Maxlength = "10" })%></td>
        <td><%= Html.TextBoxFor(model => model.DayRequested.TimeOfLeave, new { Class = "timedropdown", Maxlength = "8" })%></td>
        <td><%= Html.TextBoxFor(model => model.DayRequested.HoursRequested, new { Class = "hoursdropdown", Maxlength = "4" })%></td>
        <td><%= Html.DropDownListFor(model => model.DayRequested.RequestType, 
            new SelectList(Model.LeaveRequestType, "Value", "Text", Model.DayRequested.RequestType), "(Select)")%></td>
        <td><a href="#" class="deleteRow"><img src="../../images/site_icons/16/69.png" title="Delete" alt="Delete" border="0" /></a></td>
    <% } %>
</tr>

这是生成的表单:

<form method="post" action="/LeaveRequest/Create">
    <fieldset>
        <legend>Request Details</legend>
        <table>
            <tbody id="editorRows">
                <tr><th>Date</th><th>Time</th><th>Hours</th><th>Request Type</th><th></th></tr>
<tr class="editorRow">
    <input type="hidden" value="c43391a3-7fe4-4514-8b27-d00995d64848" autocomplete="off" name="requestedDays.index">

        <td><input type="text" value="11/17/2010" name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].DayRequested.DateOfLeave" id="requestedDays_c43391a3-7fe4-4514-8b27-d00995d64848__DayRequested_DateOfLeave" maxlength="10" class="datepicker"></td>
        <td><input type="text" value="8:00 AM" name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].DayRequested.TimeOfLeave" id="requestedDays_c43391a3-7fe4-4514-8b27-d00995d64848__DayRequested_TimeOfLeave" maxlength="8" class="timedropdown"></td>
        <td><input type="text" value="8" name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].DayRequested.HoursRequested" id="requestedDays_c43391a3-7fe4-4514-8b27-d00995d64848__DayRequested_HoursRequested" maxlength="4" class="hoursdropdown"></td>
        <td><select name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].DayRequested.RequestType" id="requestedDays_c43391a3-7fe4-4514-8b27-d00995d64848__DayRequested_RequestType"><option value="">(Select)</option>
</select></td>
        <td><a class="deleteRow" href="#"><img border="0" alt="Delete" title="Delete" src="../../images/site_icons/16/69.png"></a></td>
</tr>
<tr class="editorRow">
    <input type="hidden" value="a24b74f6-2947-4ec5-a817-f938d6fe4e24" autocomplete="off" name="requestedDays.index">
        <td><input type="text" value="11/17/2010" name="requestedDays[a24b74f6-2947-4ec5-a817-f938d6fe4e24].DayRequested.DateOfLeave" id="requestedDays_a24b74f6-2947-4ec5-a817-f938d6fe4e24__DayRequested_DateOfLeave" maxlength="10" class="datepicker"></td>
        <td><input type="text" value="8:00 AM" name="requestedDays[a24b74f6-2947-4ec5-a817-f938d6fe4e24].DayRequested.TimeOfLeave" id="requestedDays_a24b74f6-2947-4ec5-a817-f938d6fe4e24__DayRequested_TimeOfLeave" maxlength="8" class="timedropdown"></td>
        <td><input type="text" value="8" name="requestedDays[a24b74f6-2947-4ec5-a817-f938d6fe4e24].DayRequested.HoursRequested" id="requestedDays_a24b74f6-2947-4ec5-a817-f938d6fe4e24__DayRequested_HoursRequested" maxlength="4" class="hoursdropdown"></td>
        <td><select name="requestedDays[a24b74f6-2947-4ec5-a817-f938d6fe4e24].DayRequested.RequestType" id="requestedDays_a24b74f6-2947-4ec5-a817-f938d6fe4e24__DayRequested_RequestType"><option value="">(Select)</option>
</select></td>
        <td><a class="deleteRow" href="#"><img border="0" alt="Delete" title="Delete" src="../../images/site_icons/16/69.png"></a></td>
</tr>
</tbody>
    </table>
    <p><a id="addItem" href="/LeaveRequest/BlankRequestedDayRow">Add Day</a></p>

    <p>Type your time to sign your request.</p>
    <p><label for="LeaveRequest_EmployeeSignature">Employee Signature</label>: <input type="text" value="" name="LeaveRequest.EmployeeSignature" id="LeaveRequest_EmployeeSignature" class="required"></p>
    <p><label for="LeaveRequest_EmployeeComment">Employee Comment</label>: <input type="text" value="" name="LeaveRequest.EmployeeComment" id="LeaveRequest_EmployeeComment"></p>
    <p><input type="submit" value="Submit Request"></p>
</fieldset>
</form>

该表单发布以下信息:

Parametersapplication/x-www-form-urlencoded
LeaveRequest.EmployeeComm...    Comment
LeaveRequest.EmployeeSign...    Michael Wills
requestedDays.index 549a7c9a-9c7d-4032-a1cd-6bfda92bf1f2
requestedDays.index 2838b025-d971-4d98-a081-5ea0c559aebb
requestedDays[2838b025-d9...    11/17/2010
requestedDays[2838b025-d9...    8
requestedDays[2838b025-d9...    1
requestedDays[2838b025-d9...    8:00 AM
requestedDays[549a7c9a-9c...    11/17/2010
requestedDays[549a7c9a-9c...    8
requestedDays[549a7c9a-9c...    1
requestedDays[549a7c9a-9c...    8:00 AM
Source
Content-Type: application/x-www-form-urlencoded
Content-Length: 907
requestedDays.index=549a7c9a-9c7d-4032-a1cd-6bfda92bf1f2&requestedDays%5B549a7c9a-9c7d-4032-a1cd-6bfda92bf1f2%5D.DayRequested.DateOfLeave=11%2F17%2F2010&requestedDays%5B549a7c9a-9c7d-4032-a1cd-6bfda92bf1f2%5D.DayRequested.TimeOfLeave=8%3A00+AM&requestedDays%5B549a7c9a-9c7d-4032-a1cd-6bfda92bf1f2%5D.DayRequested.HoursRequested=8&requestedDays%5B549a7c9a-9c7d-4032-a1cd-6bfda92bf1f2%5D.DayRequested.RequestType=1&requestedDays.index=2838b025-d971-4d98-a081-5ea0c559aebb&requestedDays%5B2838b025-d971-4d98-a081-5ea0c559aebb%5D.DayRequested.DateOfLeave=11%2F17%2F2010&requestedDays%5B2838b025-d971-4d98-a081-5ea0c559aebb%5D.DayRequested.TimeOfLeave=8%3A00+AM&requestedDays%5B2838b025-d971-4d98-a081-5ea0c559aebb%5D.DayRequested.HoursRequested=8&requestedDays%5B2838b025-d971-4d98-a081-5ea0c559aebb%5D.DayRequested.RequestType=1&LeaveRequest.EmployeeSignature=Michael+Wills&LeaveRequest.EmployeeComment=Comment

推荐答案

看起来您可能需要从隐藏的表单字段名称中删除DayRequested.

Looks like you may need to remove DayRequested from your hidden form field name.

例如:

... I removed some of the attributes because the only thing that's changed here is the name attribute.
<input type="hidden" name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].DateOfLeave" value="11/17/2010" />
<input type="hidden" name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].TimeOfLeave" value="8:00 AM" />
<input type="hidden" name="requestedDays[c43391a3-7fe4-4514-8b27-d00995d64848].HoursRequested" value="8"  />
...

正如问题注释中所讨论的那样，ASP.NET MVC会生成您提供的源似乎很奇怪，因为这表明每个RequestedDay对象都有一个称为RequestedDay的属性.

As discussed in the question comments, it seems odd that ASP.NET MVC would generate the source you gave, as that suggests that each RequestedDay object has a single property called RequestedDay.

您要绑定到的对象称为requestedDays，并且guid指示您要绑定到集合中的哪个位置(这很明显，我知道！).因此，说明对象名称(DayRequested)没有任何意义，因为模型绑定器应该已经知道这一点，并且只需要知道它正在处理的该类的哪个属性即可.

The object you're binding to is called requestedDays, and the guid is an indication of which position in the collection you're binding to (stating the obvious here, I know!). Therefore, stating the object name (DayRequested) doesn't make any sense, since the model binder should already know this, and just needs to know which property of that class it's dealing with.

这篇关于当我期望值时，IEnumerable为null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！