获取datalist中label控件的问题

页面： 
   <asp:DataList ID="dlTop" runat="server" OnItemDataBound="dlTop_ItemDataBound">
        <HeaderTemplate>
        </HeaderTemplate>
        <ItemTemplate>
            <div style="text-align: center; padding-top: 5px; padding-bottom: 5px">
                <a class="a_title" href='<%= "ShowBBS.aspx?forum_id="%><%# Eval("forum_id") %>' target="_blank">
                    <asp:Label ID="lblTopTitle" runat="server" Text='<%# Eval("forum_header") %>'></asp:Label>
                </a>
            </div>
            <div style="float: left; padding-left: 5px; width: 100px; text-align: left">
                <asp:Label ID="lblContent" runat="server" CssClass="abstract" Text='<%# Eval("forum_content")%>'></asp:Label>
                <a class="a_he" href='<%= "ShowBBS.aspx?forum_id="%><%# Eval("forum_id") %>' target="_blank">
                    [详细]</a>
            </div>
        </ItemTemplate>
    </asp:DataList>代码：
    protected void dlTop_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.Item )
        {
            Label lblContent = (Label)e.Item.FindControl("lblContent");
            lblContent.Text = lblContent.Text.Length > 22 ? lblContent.Text.Substring(0, 22) + "..." : lblContent.Text;
        }
    }为什么标红的那行值不为true？调试看e.Item.ItemType的值为header，而ListItemType.Item的值为item