那位高手帮帮我解决这个问题

不知怎么解决，本人万分感谢！


“/”应用程序中的服务器错误。
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该字符串未被识别为有效的 DateTime。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.FormatException: 该字符串未被识别为有效的 DateTime。

源错误:


行 94:                 <asp:TemplateField HeaderText="VIP设置" >
行 95:                 <ItemTemplate>
行 96:                 <%#ReturnVIP(int.Parse(Eval("userid").ToString()))%>
行 97:                 </ItemTemplate>
行 98:                 </asp:TemplateField>
 

源文件: e:\wwwroot\qingbao\web\manager\ht\huiyuan\sjgsManager.aspx    行: 96

堆栈跟踪:


[FormatException: 该字符串未被识别为有效的 DateTime。]
   System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles) +2844850
   System.Convert.ToDateTime(String value) +98
   WebCommon.database.ReturnVip(Int32 userId) +639
   webUI.manager.ht.huiyuan.sjgsManager.ReturnVIP(Int32 userid) +15
   ASP.manager_ht_huiyuan_sjgsmanager_aspx.__DataBind__control25(Object sender, EventArgs e) in e:\wwwroot\qingbao\web\manager\ht\huiyuan\sjgsManager.aspx:96
   System.Web.UI.Control.OnDataBinding(EventArgs e) +99
   System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +92
   System.Web.UI.Control.DataBind() +15
   System.Web.UI.Control.DataBindChildren() +211
   System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +102
   System.Web.UI.Control.DataBind() +15
   System.Web.UI.Control.DataBindChildren() +211
   System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +102
   System.Web.UI.Control.DataBind() +15
   System.Web.UI.WebControls.GridView.CreateRow(Int32 rowIndex, Int32 dataSourceIndex, DataControlRowType rowType, DataControlRowState rowState, Boolean dataBind, Object dataItem, DataControlField[] fields, TableRowCollection rows, PagedDataSource pagedDataSource) +155
   System.Web.UI.WebControls.GridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) +2417
   System.Web.UI.(IEnumerable data) +57
   System.Web.UI.WebControls.GridView.PerformDataBinding(IEnumerable data) +14
   System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data) +114
   System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +31
   System.Web.UI.WebControls.DataBoundControl.PerformSelect() +142
   System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +73
   System.Web.UI.WebControls.GridView.DataBind() +4
   webUI.manager.ht.huiyuan.sjgsManager.initload(String strWhere) +257
   webUI.manager.ht.huiyuan.sjgsManager.Page_Load(Object sender, EventArgs e) +175
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627