Kendo Grid: Foreign Key Dropdown does not update grid cell after update

Question

I have a Kendo MVC grid that contains a nullable property (short) that is bound as a foreign key and uses a dropdown list as an editor template. I am also using inline editing.

When the property value is null, the dropdown list selected value does not get set into the grid cell after the update button is clicked. This works fine if incell editing is used. I am looking for a workaround that will solve my problem. I am including a stripped down version of my code below

Everything works if the nullable value is set to a non-null value.

GRID

@(Html.Kendo().Grid<AssetViewModel>()
   .Name("DealAssets")
   .Columns(c =>
   {
      c.Bound(x => x.Name);
      c.ForeignKey(x => x.AssetTypeID, (IEnumerable<SelectListItem>)ViewBag.AssetTypeList, "Value", "Text");
      c.ForeignKey(x => x.SeniorityTypeID, seniorityTypeList, "Value", "Text").EditorTemplateName("GridNullableForeignKey");
      c.ForeignKey(x => x.RateBaseID, rateBaseList, "Value", "Text").EditorTemplateName("GridNullableForeignKey"); ;
      c.Command(m => { m.Edit(); m.Destroy(); });
   })
   .ToolBar(toolbar => toolbar.Create().Text("Add New Asset"))
   .Editable(x => x.Mode(GridEditMode.InLine))
   .DataSource(ds => ds
      .Ajax()
      .Model(model => model.Id(request => request.ID))
      .Read(read => read.Action("ReadAssets", "Deal", new { id = Model.ID }))
      .Create(create => create.Action("CreateAsset", "Deal", new { currentDealID = Model.ID }))
      .Update(update => update.Action("UpdateAsset", "Deal"))
      .Destroy(destroy => destroy.Action("DeleteAsset", "Deal"))
   )
)

EDITOR TEMPLATE

@model short?
@{
   var controlName = ViewData.TemplateInfo.GetFullHtmlFieldName("");
}
@(
   Html.Kendo().DropDownListFor(m => m)
      .Name(controlName)
      .OptionLabel("- Please select -")
      .BindTo((SelectList)ViewData[ViewData.TemplateInfo.GetFullHtmlFieldName("") + "_Data"])
)

UPDATE ACTION

public ActionResult UpdateAsset([DataSourceRequest] DataSourceRequest request, int ID)
{
   var dealAsset = DataContext.DealAssets.SingleOrDefault(o => o.ID == ID);
   if (dealAsset != null)
   {
      if (TryUpdateModel(dealAsset.Asset, new[] {"Name","AssetTypeID","SeniorityTypeID","RateBaseID" }))
      {
         DataContext.SaveChanges();
      }
   }
   return Json(new[] { new AssetViewModel(dealAsset) }.ToDataSourceResult(request, ModelState), JsonRequestBehavior.AllowGet);
}

Answer 1

Telerik just recently added a new HTML attribute, data_value_primitive, to their selectlist that addresses the issue above. The new attribute should be added in the foreign key editor template and set to true.

 Html.Kendo().DropDownListFor(m => m)
        .Name(controlName)
        .OptionLabel("- Please select -")
        .BindTo((SelectList)ViewData[ViewData.TemplateInfo.GetFullHtmlFieldName("") + "_Data"])
        **.HtmlAttributes(new { data_value_primitive = true})**

This last section is a modification to the update method to account for the grid not passing back null properties when doing the ajax call. I think this has more to do with how the TryUpdateModel method works

...
if (TryUpdateModel(dealAsset.Asset, new[] {"Name","AssetTypeID","SeniorityTypeID","RateBaseID" }))
{
   // If no property passed back then set it to null
   var senorityTypeID = ValueProvider.GetValue("SeniorityTypeID");
   if (senorityTypeID == null)
   {
      dealAsset.Asset.SeniorityTypeID = null;
   } else {
      dealAsset.Asset.SeniorityTypeID = (short)senorityTypeID.ConvertTo(typeof(short));
   }
   var rateBaseID = ValueProvider.GetValue("RateBaseID");
   if (rateBaseID == null)
   {
      dealAsset.Asset.RateBaseID = null;
   } else {
      dealAsset.Asset.RateBaseID = (byte)rateBaseID.ConvertTo(typeof(byte));
   }
   DataContext.SaveChanges();
}
'''