将 Html.DisplayNameFor 与 IEnumerable<IGrouping> 一起使用

Question

我从显示值表 (IEnumerable<FooViewModel>) 切换到在 Razor 页面中显示分组值表 (IEnumerable<IGrouping<DateTime, FooViewModel>>)。

获取模型属性的显示名称的语法是@Html.DisplayNameFor(model => model.ID)。

我认为 DisplayNameFor 和 IGrouping<DateTime, FooViewModel> 使用的语法不正确，因为它只显示模型的一个属性（在本例中为 ID）：@Html.DisplayNameFor(item => item.FirstOrDefault().ElementAtOrDefault(0).ID)。

正确的语法是什么？

Answer 1

我认为你的语法是正确的！

@model IEnumerable<IGrouping<DateTime, FooViewModel>>

@if (Model.Any())
{
    /*
     * Since we've checked there are groupings, you can just use .First() to get 
     * the first group.
     *
     * .Key will give you the key you use to group things by. In this case, it's 
     * DateTime.
     *
     * Since there are groupings, there must be elements in the group so it's safe 
     * to use .ElementAt() to get to the view model, FooViewModel.
     */

    <table class="table">
        <thead>
            <tr>
                <th>@Html.DisplayNameFor(model => model.First().Key)</th>
                <th>@Html.DisplayNameFor(model => model.First().ElementAt(0).ID)</th>
            </tr>
        </thead>
        <tbody>
            @foreach (var group in Model)
            {
                <tr>
                    <td>@group.Key</td>
                    <td>@String.Join(", ", group.Select(x => x.ID))</td>
                </tr>
            }
        </tbody>
    </table>
}

还有假数据：

public class FooViewModel
{
    [Display(Name = "Date time")]
    public DateTime DateTime { get; set; }

    [Display(Name = "Haha ID")]
    public int ID { get; set; }
}

var data = new List<FooViewModel>
{
    new FooViewModel { DateTime = new DateTime(2019, 06, 25), ID = 1 },
    new FooViewModel { DateTime = new DateTime(2019, 06, 25), ID = 2 },
    new FooViewModel { DateTime = new DateTime(2019, 06, 24), ID = 3 },
    new FooViewModel { DateTime = new DateTime(2019, 06, 23), ID = 4 }
};

应该是这样的：