GridView的SelectedIndexChanged事件不被触发，而是弹出javascript:__doPostBack('gvwList','Selec

这是前台代码
<%@ Page Language="C#"........ EnableEventValidation="false"%>

.........
                <asp:GridView ID="gvwList" runat="server" SkinID="skigridview1" AutoGenerateColumns="False" DataKeyNames="wftyno"
                    EnableViewState="False" AutoPostBack="true" EmptyDataText="No data found" Width="100%"
                    OnSelectedIndexChanged="gvwList_SelectedIndexChanged">
                    <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
                    <Columns>
                        <asp:BoundField DataField="wfty" HeaderText="Wafer Type">
                            <HeaderStyle Wrap="False" Width="100px" HorizontalAlign="Left" />
                            <ItemStyle Wrap="False" />
                        </asp:BoundField>
                        <asp:BoundField DataField="capt" HeaderText="Capacity">
                            <HeaderStyle Wrap="False" HorizontalAlign="Left" Width="100px" />
                            <ItemStyle Wrap="False" />
                        </asp:BoundField>
                        <asp:CommandField ShowSelectButton="True" ShowCancelButton="False">
                            <HeaderStyle Width="50px" Wrap="False" />
                            <ItemStyle ForeColor="Blue" />
                        </asp:CommandField>
                    </Columns>
                    <SelectedRowStyle BackColor="DodgerBlue" Font-Bold="True" ForeColor="White"  />
                </asp:GridView>
后台就是
  protected void gvwList_SelectedIndexChanged(object sender, EventArgs e)
    {
        txtwfty.Text = gvwList.Rows[gvwList.SelectedIndex].Cells[0].Text;
    }
这个网页是经showModalDialog打开的

补充：.NET技术 ,  ASP.NET