第一次提问题－－根据dropdownlist 的选择而动态显示或隐藏GridView的某些字段！！

我上网找了一些资料，但还是没有解决，只有请教csdn的各位大神们了！

问题如下：

dropdownlist 有四个选项，当我选择人物和宠物时，隐藏字段：GoodType





前台代码如下：

<asp:GridView ID="GridView1" runat="server" AllowPaging="True"
AutoGenerateColumns="False" DataKeyNames="Id" DataSourceID="SqlDataSource2"
Width="98%">
<Columns>
<asp:DynamicField DataField="Id" HeaderText="Id" Visible="False" />
<asp:BoundField DataField="Title" HeaderText="Title" SortExpression="Title" />
<asp:BoundField DataField="Photo" HeaderText="Photo" SortExpression="Photo" />
<asp:BoundField DataField="GoodType" HeaderText="GoodType"
SortExpression="GoodType" />
<asp:BoundField DataField="TypeId" HeaderText="TypeId"
SortExpression="TypeId" Visible="False" />
<asp:BoundField DataField="Area" HeaderText="Area" SortExpression="Area" />
<asp:BoundField DataField="UserName" HeaderText="UserName"
SortExpression="UserName" />
<asp:BoundField DataField="Email" HeaderText="Email" SortExpression="Email" />
<asp:BoundField DataField="QQ" HeaderText="QQ" SortExpression="QQ" />
<asp:BoundField DataField="Detail" HeaderText="Detail"
SortExpression="Detail" />
<asp:BoundField DataField="PhoneNum" HeaderText="PhoneNum"
SortExpression="PhoneNum" />
<asp:BoundField DataField="Time" DataFormatString="{0:yyyy-mm-dd}"
HeaderText="Time" ReadOnly="True" SortExpression="Time" />
</Columns>
</asp:GridView>

后台如何在dropdownlist选项改变时动态显示或者隐藏GoodType这个字段！