问使用.where扩展方法导致重复(MVC-LINQ)

EN

[ChildActionOnly]
public ActionResult someAction(string itemID = "")
{
    //Empty itemID
    if(string.IsNullOrEmpty(itemID))
    {
        return RedirectToAction("Index", "Search");
    }

    var model = _db.someTable
            .Where(r => r.itemID == itemID)
            .OrderBy(r => r.col1)
            .ThenBy(r => r.col2)
            .Take(20);
    return PartialView("_myView", model);
}

@model IEnumerable<MyApp.Models.OperationData>
.
.
.
@foreach (var item in Model) {
<tr>
    <td>
        @Html.DisplayFor(modelItem => item.some column)
    </td>
.
.
.

var model = from r in _db.someTable where r.itemID == itemID select r;