C＃ASP.NET MVC视图下拉编译错误CS0161

Question

@model IEnumerable<Calendar.Models.CheckDays

<p>
    @using (Html.BeginForm())
    {
        <table>
            <tr>
                <th>
                    @Html.ActionLink("Create New", "Create")
                </th>
                <th>
                    @Html.DropDownListFor(model => model.DayOfWeek, htmlAttributes: new { @class = "form-control" })
                </th>
                <th>
                    <input type="button" value="Search" />
                </th>
            </tr>

        </table>
    }

</p>
   <tr>
        <th>
            @Html.DisplayNameFor(model => model.DayOfWeek)
        </th>

    </tr>

    @foreach (var item in Model)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.DayOfWeek)
            </td>
            </td>
        </tr>
    }

I'm trying to create a drop down list so I can filter the the index results but I keep getting an error

"Compiler Error Message: CS1061: 'IEnumerable' does not contain a definition for 'DayOfWeek' and no extension method 'DayOfWeek' accepting a first argument of type 'IEnumerable' could be found (are you missing a using directive or an assembly reference?)"

The line that errors out is

  Html.DropDownListFor(model => model.DayOfWeek, htmlAttributes: new { @class = "form-control" })".

Do I need to do something in the model or do I have syntax errors?

Answer 1

You misunderstood what first parameter is for. It is to point where selected item should go for. It is for selectedItem variable. Check this blog post: https://odetocode.com/blogs/scott/archive/2013/03/11/dropdownlistfor-with-asp-net-mvc.aspx . You have to create separate class for model with list of elements and variable SelectedDayOfWeek.

Model class:

public class CheckDaysViewModel 
{
  public IEnumerable<CheckDays> CheckDays {get;set;}
  public IEnumerable<SelectListItem> CheckDaysAsSelectedList => this.CheckDays.Select(e => new SelectListItem(e.DayOfWeek, e.DayOfWeek));
  public CheckDays SelectedDay {get;set;}

}

cshtml

@model CheckDaysViewModel

<p>
    @using (Html.BeginForm())
    {
        <table>
            <tr>
                <th>
                    @Html.ActionLink("Create New", "Create")
                </th>
                <th>
                    @Html.DropDownListFor(m => m.SelectedDay, Model.CheckDaysAsSelectedList, null, htmlAttributes: new { @class = "form-control" })
                </th>
                <th>
                    <input type="submit" value="Search" />
                </th>
            </tr>

        </table>
    }
</p>

<table>

<tr>
    <th>
        @Html.DisplayNameFor(m => m.CheckDays.First().DayOfWeek)
    </th>
</tr>

    @foreach (var item in Model.CheckDays)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.DayOfWeek)
            </td>
        </tr>
    }

</table>