asp.net webforms model binding a checkbox to boolean array in a Gridview EditItemTemplate

I have a Gridview EditItemTemplate containing individual checkboxes for the days of the week. Seven in total.

Is it possible, or, is there a nice way to do model binding to save the selected value of these checkboxes to an array of bools in my GridView UpdateMethod?

With the code here I get a HttpException when I hit the Edit Button on a row of my Gridview:

DataBinding: 'WebTest3.Data.MyModel' does not contain a property with the name 'true'.

GridView Update method :

 public void EditSchedule(int ScheduleId)
    {

        MyModel model = new MyModel();


        TryUpdateModel(model);
        if (ModelState.IsValid)
        {
            _repo.UpdateSchedule(model);
            _repo.Save();
        }


        Response.Redirect(Request.RawUrl);

My simplified model looks like:

public class MyModel
    {
        public int ScheduleId { get; set: }
        public string[] Days { get; set; }
    }

My markup looks like:

<EditItemTemplate>
        <tr>
            <td class="cell cellButtons">
                <asp:Button ID="InserButton" runat="server" Text="Insert" CommandName="Update" CausesValidation="true" validationgroup="GridGroup" />
                <asp:Button ID="btnCancel" runat="server" Text="Cancel" CommandName="Cancel"  CausesValidation="false" />
            </td>

             <td class="cell cellDay">
                <asp:CheckBox ID="cbM" runat="server" checked='<%# BindItem.Days[0] %>' />
            </td>

            <td class="cell cellDay">
                <asp:CheckBox ID="cbT" runat="server" checked='<%# BindItem.Days[1] %>' />
            </td>

            <td class="cell cellDay">
                <asp:CheckBox ID="cbW" runat="server" checked='<%# BindItem.Days[2] %>' />
            </td>
            .
            .
            .
        </tr>
</EditItemTemplate>    

The checkboxes display ok on my page and hit the EditMethod ok (with the correct ScheduleId..nice)) if I use 'Item' instead of 'BindItem' :

<asp:CheckBox ID="cbW" runat="server" checked='<%# Item.Days[0] %>' />

But then of course won't save when I do the TryUpdateModel(model) thing.

If I have separate, single bool values for each day of the week in my model then it all works. I just thought it might be straighforward to do with collections also. With the collections I can simplify my markup with repeaters and that kind of thing.

Would a checklist instead of checkboxes do anything for me ?

Thanks in advance for your wisdom,