将数据表绑定到自定义GridView控件会生成null引用异常

我在将数据表绑定到自定义gridview控件时遇到问题。我遇到的问题是在数据绑定到控件时出现nullreference异常。

当数据源是由SqlDataAdapter填充的数据表时，gridview绑定时不会出现问题。以下是适用于我的代码：

    public override void Load(DateTime startDate, DateTime endDate)
    {
        using (DataTable dt = new DataTable())
        {
            using (dbCheckpointWarehouseDataContext thisDataContext = new dbCheckpointWarehouseDataContext())
            {
                var qryItemCount = [LINQ QUERY THAT WORKS FINE.]
                using (SqlCommand cmd = thisDataContext.GetCommand(qryItemCount) as SqlCommand)
                {
                    using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
                    {
                        adapter.Fill(dt);
                    }
                    if (dt.Rows.Count > 0)
                    {
                        CustomGridView cgvResults = new CustomGridView();
                        cgvResults.AddBoundField("DistrictManagerName", "District Manager", "");
                        cgvResults.AddBoundField("newMetric", "newMetric", "");
                        cgvResults.DataSource = dt;
                        cgvResults.DataBind();
                        m_ReportHTMLString = Utilities.RenderHTMLStringOfControl(cgvResults);
                    }
                }
            }
        }
    }

如果我试图用强类型数据表加载相同的自定义控件，我会得到null引用异常。在我将数据表绑定到股票网格视图控件的地方，有三行注释掉了。这也是有效的。只有当我在自定义网格视图中使用强类型数据表时，我才会遇到这个问题。该异常是在DataBind（）方法中生成的。在调试模式中，我已经验证了数据表不是空的，并且在设置DataSource属性时没有异常。这是生成空引用的代码：

    public override void Load(DateTime startDate, DateTime endDate)
    {
        using (DataTable dt = new DataTable())
        {
            dt.Columns.Add("DistrictManagerName", typeof(string));
            dt.Columns.Add("newMetric", typeof(Int32));
            DataRow row;
            using (dbCheckpointWarehouseDataContext thisDataContext = new dbCheckpointWarehouseDataContext())
            {
                var qryItemCount = [LINQ QUERY THAT WORKS FINE.]
                                  .AsEnumerable()
                                  .Select([SELECT STATEMENT THAT WORKS FINE])

                foreach (var rowtrans in qryTest)
                {
                    row = dt.NewRow();
                    row["DistrictManagerName"] = rowtrans.DistrictManagerName;
                    row["newMetric"] = Convert.ToInt32(rowtrans.newMetric);
                    dt.Rows.Add(row);
                }
                string total = dt.Compute("Sum(newMetric)", "").ToString();
                row = dt.NewRow();
                row["DistrictManagerName"] = "Total";
                row["newMetric"] = String.Format("{0:#,0}", total);
                dt.Rows.Add(row);
                dt.AcceptChanges();
                CustomGridView cgvResults = new CustomGridView();
                cgvResults.AddBoundField("", "District Manager", "");
                cgvResults.AddBoundField("", "Total", "");
                cgvResults.DataSource = dt;
                cgvResults.DataBind();
                //GridView cgvResults = new GridView();
                //cgvResults.DataSource = dt.DefaultView;
                //cgvResults.DataBind();
                m_ReportHTMLString = Utilities.RenderHTMLStringOfControl(cgvResults);
            }
        }
    }

以下是自定义网格视图控件的代码：

    public CustomGridView() : base()
    {
        AutoGenerateColumns = true;
        AllowPaging = true;
        AllowSorting = true;
        PageSize = 25;
        GridLines = GridLines.Vertical;
        CssClass = "gridView";
        HeaderStyle.CssClass = "gridViewHeader";
        RowStyle.CssClass = "gridViewRow";
        AlternatingRowStyle.CssClass = "gridViewAlternatingRow";
        PagerStyle.CssClass = "gridViewPager";
        CellPadding = 3;
    }
    public void AddBoundField(string dataField, string headerText, string sortExpression)
    {
        BoundField bf = new BoundField();
        if (dataField != "")
        {
            bf.DataField = dataField;
        }
        if (headerText != "")
        {
            bf.HeaderText = headerText;
        }
        if (sortExpression != "")
        {
            bf.SortExpression = sortExpression;
        }
        Columns.Add(bf);
    }

谢谢你能提供的任何帮助。

AllowPaging = true

AllowPaging = false