为什么DetailsView中的DetailsView1_ItemUpdated事件 我都调用不到呀？

前台代码:
<asp:DetailsView ID="DetailsView1" runat="server" Height="50px" Width="125px"
onitemupdated="DetailsView1_ItemUpdated"
onitemupdating="DetailsView1_ItemUpdating"
onmodechanging="DetailsView1_ModeChanging">
<Fields>
<asp:TemplateField ShowHeader="False">
<EditItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="True"
CommandName="Update" Text="更新"></asp:LinkButton>
 <asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False"
CommandName="Cancel" Text="取消"></asp:LinkButton>
</EditItemTemplate>
<ItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False"
CommandName="Edit" Text="编辑"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
</Fields>
</asp:DetailsView>

后台代码：
UsersLogic bll = new UsersLogic();
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
dvData();
}
}
protected void DetailsView1_ModeChanging(object sender, DetailsViewModeEventArgs e)
{
DetailsView1.ChangeMode(e.NewMode);
dvData();
}
private void dvData()//绑定数据
{
DetailsView1.DataSource = bll.GetModelList("Id=2");
DetailsView1.DataBind();
}
protected void DetailsView1_ItemUpdating(object sender, DetailsViewUpdateEventArgs e)
{
//MessageHelper.Alert(this, "sss");

//e.Cancel = true ;

//dvData();

}

protected void DetailsView1_ItemUpdated(object sender, DetailsViewUpdatedEventArgs e)
{

DetailsView1.ChangeMode(DetailsViewMode.ReadOnly);
}

这里 DetailsView1_ItemUpdated都调用不到 请问是怎么回事呀！我找了好久 还是不知道哪里出问题了？？
请各位高手帮帮忙！！