为什么找不到控件解决方法

为什么找不到控件
我看书上写的，怎么找不到控件

private   void   dgrdReplies_ItemDataBound(object   sender,   System.Web.UI.WebControls.DataGridItemEventArgs   e)
{
LinkButton   lbtnDeleteReply   =   (LinkButton)e.Item.FindControl( "lbtnDeleteReply ");
if(lbtnDeleteReply   !=   null)
{
lbtnDeleteReply.Attributes.Add( "onclick "   , "return   confirm( '你真的要删除此回复吗? '); ");
}
}


[解决办法]
private void dgrdReplies_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
{
if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
LinkButton lbtnDeleteReply = (LinkButton)e.Item.FindControl( "lbtnDeleteReply ");
if(lbtnDeleteReply != null)
{
lbtnDeleteReply.Attributes.Add( "onclick " , "return confirm( '你真的要删除此回复吗? '); ");
}
}
}