ASP.Net MVC EditorFor not working

I am trying to render a table, using EditorFor, and a partialview, I think.

I have a model with a List<> property defined like this:

public List<TransactionSplitLine> TransactionSplitLines { get; set; }

The idea is that a user selects a few drop downs and enters a value into an edit box, and clicks a button. The model goes back to the controller, and the controller adds the entered values to the List<>

[HttpPost]
public ActionResult AccountTransaction(AccountTransactionView model)
{
    var reply = CreateModel(model);
    if (model.CategoryIds != null)
    {
        foreach (var c in model.CategoryIds)
        {
            reply.TransactionSplitLines.Add(new TransactionSplitLine { Amount = "100", Category = "Test Category", SubCategory = "Test More", CategoryId = int.Parse(c) });
        }
    }
    reply.TransactionSplitLines.Add(new TransactionSplitLine { Amount = "100", Category = "Test Category", SubCategory = "Test More", CategoryId = 1 });
    return View("AccountTransaction", reply);
}

Ignore the CreateModel. It simply sets up some data. Also, I am hardcoding data. This will eventually come from some form values.

The model is then returned to the same screen, allowing the user to ender more data. Any items in the List<> are read and a Table is rendered. I also have to store the current listen item values in hidden fields, so that they can be submitted back, along with the new data entered, so that the list can grow each time the user adds data.

The view is defined like this:

<table width="600">
    <thead>
        <tr class="headerRow">
            <td>
                Category
            </td>
            <td>
                Sub Category
            </td>
            <td>
                Amount
            </td>
        </tr>
    </thead>
    <tbody>
        <%=Html.EditorFor(m=>m.TransactionSplitLines) %>
    </tbody>
</table>

This is my first attempt with EditorFor...

My View is in a folder 'Views/BankAccount/AccountTransaction.aspx

I have created a ascx in Views/Shared/TransactionSplitLines.ascx

The code for the ascx is like this:

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<BudgieMoneySite.Models.TransactionSplitLine>" %>


<tr>
    <td>
        <%=Model.Category %>
        <%=Html.HiddenFor(x => x.CategoryId)%>
    </td>
    <td>
        <%=Model.SubCategory %>
        <%=Html.HiddenFor(x => x.SubCategoryId)%>
    </td>
    <td>
        <%=Model.Amount %>
        <%=Html.HiddenFor(x => x.AmountValue)%>
    </td>

</tr>

This is data

The 'This is data' is just test stuff, which is never rendered.

When I run this, all that happens is that my output is rendered as:

<table width="600">
    <thead>
        <tr class="headerRow">

            <td>
                Category
            </td>
            <td>
                Sub Category
            </td>
            <td>
                Amount
            </td>
        </tr>

    </thead>
    <tbody>
        Test Category
    </tbody>
</table>

It seems like the ascx isn't being used? I'd expect to see the 'This is data' text. But, nothing. Hopefully you can see an obvious fault?