为何我的DataGrid的RenderControl之后，STRINGWRITER接收不到任何信息

[mathewyang]

DataGrid3绝对有数据，但是strOutput就接收不到任何信息。

Private Function cbfExportExcel(ByVal dt As Data.DataTable) As String
Dim strOutput As String
Response.ClearHeaders()
Response.ContentType = "text/plaincharset=gb2312"
Response.AddHeader("content-disposition", String.Format("attachment filename= {0}", HttpUtility.UrlEncode("Excel.csv")))
DataGrid3.DataSource = dt.DefaultView
DataGrid3.DataBind()

Me.EnableViewState = False
Dim tw As New System.IO.StringWriter()
Dim hw As New System.Web.UI.HtmlTextWriter(tw)

Me.DataGrid3.RenderControl(hw)
strOutput = tw.ToString()‘’接收不到任何信息
Response.Write(tw) '('strOutput)
Response.End()
Return ""

end function