MVC Razor编辑器用于列表中的最后一个对象

Question

I'm trying to display EditorFor for the last child Object in an collection. Below are the POCOs for the Order (Parent) and Hold (child collection):

public class Order
{
    public int ID {get;set;}
    public string Name {get;set;}
    ....
    public virtual List<Hold> Holds { get; set; }
}

public class Hold
{
    public int ID { get; set; }
    public int OrderID { get; set; }
    public virtual Order Order { get; set; }
    public DateTime? When { get; set; }
    public string Reason { get; set; }
}

Here's my attempt at creating an Order view that shows an Order and the last Hold if there is one present. I've commented out the last Hold attempt that doesn't work.

@model Order

@using (Html.BeginForm("Update", "Order", FormMethod.Post, new {}))
{
   <div class="form-group row">
      @Html.LabelFor(x => x.Name, new { @class = "col-xs-2" })
      <div class="col-xs-10">
         @Html.EditorFor(x => x.Name, new { @class = "form-control"})
      </div>
   </div>

   <div class="form-group row">
      <label class="col-xs-2">When</label>
      <div class="col-xs-10">
         @*@Html.EditorFor(x => x.Holds.Last().When, new {})*@
      </div>
   </div>
}

The Holds collection can also be null so doing Last() in that case will case an null exception even if that did work.

This seems like something simple and I have this pattern in a couple places in my database. Can anyone recommend a good way to handle this situation?

Thanks!

Answer 1

You should use a view model for this because you wont get a very good response in your HttpPost action when you post this back

public class OrderViewModel
{
    public OrderViewModel()
    {
        Order = new Order();
        Hold = new Hold();
    }
    public Order Order { get; set; }
    public Hold Hold { get; set; }
}

public ActionResult Edit(int id)
{

    var o = from o context.Order.Include("Holds").Single(id);
    var model = new OrderViewModel()
    {
        Order = o
    }
    if (o.Holds.Count() > 0)
        model.Hold = o.Holds.Last();
    return View(model);
}

then just use EditorFors

@model OrderViewModel

@using (Html.BeginForm("Update", "Order", FormMethod.Post, new {}))
{
   <div class="form-group row">
      @Html.LabelFor(x => x.Order.Name, new { @class = "col-xs-2" })
      <div class="col-xs-10">
         @Html.EditorFor(x => x.Order.Name, new { @class = "form-control"})
      </div>
   </div>

   <div class="form-group row">
      <label class="col-xs-2>When</label>
      <div class="col-xs-10">
         @Html.EditorFor(x => x.Hold.When)
      </div>
   </div>
}

Answer 2

First, instead of using Last() you should use LastOrDefault() and then do proper null-checking. Last() raises an exception is nothing is found, while LastOrDefault simply returns null in that case.

Second, using Last() or LastOrDefault() will not generate the proper input names via EditorFor , so once you post, the modelbinder won't know what to do with the value. Instead, you need to use indexing:

@if (Model.Holds.Any())
{
    var lastIndex = Model.Holds.Count() - 1;

    <div class="form-group row">
        <label class="col-xs-2">When</label>
        <div class="col-xs-10">
            @Html.EditorFor(x => x.Holds[lastIndex].When, new {})
        </div>
    </div>
}