在ASP.NET MVC中发布后，Model.List为null

Question

I know there's other questions about this, but I want a better explanation about it.

I want to show a table with my Model.List and after POST I still need to access that list. Today this is not happening.

This is my cshtml:

@foreach (var student in Model.ListSchedulingDetails)
    {
        <tr>
            <td width="150">
                @Html.DisplayFor(modelItem => student.SchedulingDate)
            </td>
            <td width="250">
                @Html.DisplayFor(modelItem => student.TeacherName)
            </td>
            <td width="250">
                @Html.DisplayFor(modelItem => student.StudentName)
            </td>
            <td width="150">
                @Html.DisplayFor(modelItem => student.SchedulingHour)
            </td>
            <td width="250">
                @Html.DisplayFor(modelItem => student.SchedulingObservation)
            </td>
        </tr>
    }

After POST, my Model.ListSchedulingDetails is null. What's happening?

Answer 1

There are two things here:

1. DisplayFor() is for only displaying. For posting, we need input elements like HiddenFor() , TextBoxFor()

2. you would need to index them for posting back in case of collections, foreach wouldn't help

Your code would need to be like:

 @for (int i=0; i< Model.ListSchedulingDetails.Count; i++)
 {
     <tr>
        <td width="150">
            @Html.DisplayFor(modelItem => ListSchedulingDetails[i].SchedulingDate)
            @Html.HiddenFor(modelItem => ListSchedulingDetails[i].SchedulingDate)
        </td>
        <td width="250">
            @Html.DisplayFor(modelItem => ListSchedulingDetails[i].TeacherName)
            @Html.HiddenFor(modelItem => ListSchedulingDetails[i].SchedulingDate)
        </td>
        <td width="250">
            @Html.DisplayFor(modelItem => ListSchedulingDetails[i].StudentName)
           @Html.HiddenFor(modelItem => ListSchedulingDetails[i].SchedulingDate)
        </td>
        <td width="150">
           @Html.DisplayFor(modelItem => ListSchedulingDetails[i].SchedulingHour)
           @Html.HiddenFor(modelItem => ListSchedulingDetails[i].SchedulingDate)
        </td>
        <td width="250">
            @Html.DisplayFor(modelItem => ListSchedulingDetails[i].SchedulingObservation)
            @Html.HiddenFor(modelItem => ListSchedulingDetails[i].SchedulingDate)
        </td>
    </tr>
 }