向WebGrid添加一行显示数据绑定错误

Question

我的网络网格有3列，所有3列都有下拉列表。我正在克隆最后一行并将其附加到webgrid。它追加，并且数据也绑定到新追加的行。但是显示了视图错误“必须先绑定数据源，然后才能执行此操作”。我正在共享代码。 任何帮助表示赞赏...

模型

public class HeaderInfo
{
    public List<Header> HeaderModel { get; set; }
}
public class Header
{
    public SelectList Xaxis { get; set; }
    public SelectList Yaxis { get; set; }
    public SelectList Zaxis { get; set; }
}
public class XStatus
{
    public int ID { get; set; }
    public string StatusName { get; set; }
}
public class YStatus
{
    public int ID { get; set; }
    public string StatusName { get; set; }
}
public class ZStatus
{
    public int ID { get; set; }
    public string StatusName { get; set; }
}

控制器

public class GraphController : Controller
{
    // GET: Graph
    public ActionResult Index()
    {
       // HeaderInfo h = new HeaderInfo();
        PlotModel m = new PlotModel();
        m.h.HeaderModel = HeaderDetails();
        return View(m);
    }
    public List<Header> HeaderDetails()
    {
        List<Header> obj = new List<Header>();
        obj.Add(new Header { Xaxis = GetXfield(), Yaxis = GetYfield(), Zaxis = GetZfield() });
        return obj;
    }
    public SelectList GetXfield()
    {
        List<XStatus> status = new List<XStatus>();
        status.Add(new XStatus { ID = 1, StatusName = "aaa" });
        status.Add(new XStatus { ID = 2, StatusName = "aaa" });
        status.Add(new XStatus { ID = 3, StatusName = "aaa" });
        status.Add(new XStatus { ID = 4, StatusName = "bbb" });
        status.Add(new XStatus { ID = 5, StatusName = "aaa" });
        status.Add(new XStatus { ID = 6, StatusName = "nnn" });
        status.Add(new XStatus { ID = 7, StatusName = "mmm" });
        SelectList obj = new SelectList(status, "ID", "StatusName");
        return obj;
    }
    public SelectList GetYfield()
    {
        List<XStatus> status = new List<XStatus>();
        status.Add(new XStatus { ID = 1, StatusName = "aaa" });
        status.Add(new XStatus { ID = 2, StatusName = "aaa" });
        status.Add(new XStatus { ID = 3, StatusName = "aaa" });
        status.Add(new XStatus { ID = 4, StatusName = "bbb" });
        status.Add(new XStatus { ID = 5, StatusName = "aaa" });
        status.Add(new XStatus { ID = 6, StatusName = "nnn" });
        status.Add(new XStatus { ID = 7, StatusName = "mmm" });
        SelectList obj = new SelectList(status, "ID", "StatusName");
        return obj;
    }
    public SelectList GetZfield()
    {
        List<XStatus> status = new List<XStatus>();
        status.Add(new XStatus { ID = 1, StatusName = "aaa" });
        status.Add(new XStatus { ID = 2, StatusName = "aaa" });
        status.Add(new XStatus { ID = 3, StatusName = "aaa" });
        status.Add(new XStatus { ID = 4, StatusName = "bbb" });
        status.Add(new XStatus { ID = 5, StatusName = "aaa" });
        status.Add(new XStatus { ID = 6, StatusName = "nnn" });
        status.Add(new XStatus { ID = 7, StatusName = "mmm" });
        SelectList obj = new SelectList(status, "ID", "StatusName");
        return obj;
    }

查看

<script type="text/javascript">
    $('#clickToAdd').click(function () {
        
        var newrow = $("#grid1 tbody tr:last").clone();        
        $("#grid1 tbody").append(newrow);
    })
</script>

@{
    ViewBag.Title = "title";
    Layout = "~/Views/Shared/_Layout.cshtml";
    WebGrid g_style = new WebGrid(source:Model.h.HeaderModel);
}
<div class="row" id="grid1">            
                    
                    @g_style.GetHtml(
                   tableStyle:"gridTable",
                   headerStyle: "gridHead",
                   footerStyle: "gridFooter",
                   rowStyle: "gridRow", alternatingRowStyle: "gridAltRow",

            columns: g_style.Columns(
                g_style.Column(header:"Xaxis", format:@item=>Html.DropDownList("value", (IEnumerable<SelectListItem>)Model.h.HeaderModel[0].Xaxis)),
                g_style.Column(header: "Yaxis", format: @item => Html.DropDownList("value", (IEnumerable<SelectListItem>)Model.h.HeaderModel[0].Yaxis)),
                g_style.Column(header: "Zaxis", format: @item => Html.DropDownList("value", (IEnumerable<SelectListItem>)Model.h.HeaderModel[0].Zaxis))
                ))
                
            </div><input type="submit" value="Add new Trace" id="clickToAdd" />