在Gridview Pager中动态添加页面大小下拉列表

我有一个Gridview，必须在Pager行的运行时为其添加下拉列表。我已经在Gridview RowCreated上添加了以下代码。

protected void gv_transaction_RowCreated(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.Pager)
    {
        using (DropDownList ddlpagesize = new DropDownList())
        {
            ddlpagesize.Items.Add("25");
            ddlpagesize.Items.Add("50");
            ddlpagesize.Items.Add("75");
            ddlpagesize.Items.Add("100");
            ddlpagesize.Items.Add("150");
            ddlpagesize.Items.Add("200");
            ddlpagesize.AutoPostBack = true;
            ddlpagesize.Items.FindByText(gv_transaction.PageSize.ToString()).Selected = true;
            ddlpagesize.SelectedIndexChanged += ddlpagesize_SelectedIndexChanged;
            using (Table tbl = (Table)e.Row.Cells[0].Controls[0])
            {
                using (TableCell cell = new TableCell())
                {
                    cell.Controls.Add(new LiteralControl("<b>Page Size: </b>"));
                    cell.Controls.Add(ddlpagesize);
                    tbl.Rows[0].Cells.AddAt(0, cell);
                }
            }
        }
    }
}
protected void ddlpagesize_SelectedIndexChanged(object sender, EventArgs e)
{
    using (DropDownList ddlpagesize = (DropDownList)sender)
    {
        gv_transaction.PageSize = int.Parse(ddlpagesize.SelectedValue);
        gv_transaction.PageIndex = 0;
        BindTransactionGrid();
    }
}

现在，当我更改dropdownlist值时，SelectedIndex更改事件不会触发。但有趣的是，当我从页面大小的Dropdownlist的初始化中删除using语句时；所选的索引事件正在完美启动。请告诉我，对于Gridview 中的动态下拉列表，丢弃dropdownlist和selectedIndex Changed事件是否有任何关系