Why are my text fields getting wiped out?

Question

I've got a partial that is called by Ajax to add new line items. If I type in some data in the part ID field then click the link to Add another item, it wipes out what I just typed.

View:

<label>Parts Used
<%= Ajax.ActionLink("Add another item", "BlankEditor", new AjaxOptions {
UpdateTargetId = "partusageitems", InsertionMode = InsertionMode.InsertAfter}) %>
</label>

<div id="partusageitems">
        <% foreach (var part in Model.PartUsage)
           {
               Html.RenderPartial("~/Views/Fsr/_PartsUsage.ascx", part);
           }%>
</div>

Partial:

<div>
<% var fieldPrefix = "PartUsage[]."; %>
Part ID: <%= Html.TextBox(fieldPrefix + "ID", Model.ID, new { size = "25"})%>
Serial Number: <%= Html.TextBox(fieldPrefix + "Serial", Model.Serial, new { size = "25" })%>   
Quantity: <%= Html.TextBox(fieldPrefix + "Quantity", Model.Quantity, new { size = "10"}) %>
<a href="#partsusagesection" onclick="deleteContainer(event)">Delete</a>
</div>

Controller:

public ActionResult BlankEditor()
{
    return View("_PartsUsage", new Part());
}

Answer 1

This may just be a typo, but Partial is missing a DIV closing tag at the end.