ASP.NET:如何在DataBind期间设置Control的css类？

使用asp:Repeater生成表行:

   
      ...
   

现在在数据绑定中我想用不同的css类标记"未读"的公告,这样网络人就可以执行他想要区分读取和未读公告的任何样式:

protected void announcementsRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
   if (e.Item.ItemType != ListItemType.Item && e.Item.ItemType != ListItemType.AlternatingItem)
      return;

   // get the associated data item
   Announcement announcement = (Announcement)e.Item.DataItem;

   WebControl row = (WebControl)e.Item.FindControl("announcementRow");
      if (row != null)
         row.CssClass = row.CssClass + " announcementItemUnread";
}

除了演员在运行时失败:

System.InvalidCastException occurred
  Message="Unable to cast object of type 'System.Web.UI.HtmlControls.HtmlTableRow' to type 'System.Web.UI.WebControls.WebControl'."

事实证明,HtmlTableRow有一个不同的父母heirarchy比WebControl:

HtmlTableRow
   : HtmlContainerControl
      : HtmlControl
         : System.Web.UI.Control

这最终是WebControl的来源

WebControl
   : System.Web.UI.Control

所以我更改了代码以尝试使用System.Web.UI.Control:

Control row = (Control)e.Item.FindControl("announcementRow");
if (row != null)
   row.CssClass = row.CssClass + " announcementItemUnread";

但Control不包含以下定义CssClass:

'System.Web.UI.Control' does not contain a definition for 'CssClass'    

那么如何在DataBind期间为元素设置css类名？

   HtmlControl htmlRow = (HtmlControl)row; 
   htmlRow.Attributes["class"] = htmlRow.Attributes["class"] + " announcementItemUnread";