ExtJs Excel导出并下载IIS服务器端遇到的问题

//输出报表
function ExportReport(title) {
var vExportContent = Ext.getCmp("gridPanel").getExcelXml(null, title);
if (Ext.isIE6 || Ext.isIE7 || Ext.isSafari || Ext.isSafari2 || Ext.isSafari3 || Ext.isIE8) {
// var frm = document.createElement('form');
// frm.id = 'frmExtjs';
// frm.className = 'x-hidden';
// document.body.appendChild(frm);
var f = document.createElement("form");
f.id = "frmExtjs";
document.body.appendChild(f);
var i = document.createElement("input");
i.type = "hidden";
i.id = "exportContent";
i.name = "exportContent";
f.appendChild(i);
i.value = vExportContent;
Ext.Ajax.request({
url: 'frmExcel.aspx',
method: 'POST',
form: Ext.get('frmExtjs'),
isUpload: true,
params: { FileName: title + '.xls' }
})
} else {
document.location = 'data:application/vnd.ms-excel;base64,' + Base64.encode(vExportContent);
}

string tmpFileName = "export.xls";
string tmpContent = Request["ExportContent"];
if (Request["FileName"] != "")
{
tmpFileName = Request["FileName"];//获取传递来的文件名?
tmpFileName = System.Web.HttpUtility.UrlEncode(Request.ContentEncoding.GetBytes(tmpFileName));//处理中文文件名的情况
}
Response.Clear();
Response.Buffer = true;
Response.ContentType = "application/vnd.ms-excel";
Response.AddHeader("Content-Disposition", "attachment;filename=\"" + tmpFileName + "\"");
Response.Charset = "";
System.IO.StringWriter tmpSW = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter tmpHTW = new System.Web.UI.HtmlTextWriter(tmpSW);
tmpHTW.WriteLine(tmpContent);
Response.Write(tmpSW.ToString());
Response.End();