protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)    {        if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)        {            DataRowView row = e.Item.DataItem as DataRowView;            if (row["NickName"].ToString().Length > 4)            {                Label label = e.Item.FindControl("LabelName") as Label;                label.ForeColor = Color.Red;            }        }    }

服务端控件数据绑定时属性必须用单引号''

<asp:Label ID="LabelName" runat="server" Text='<%#Eval("NickName") %>' />

还可以参考