use http header
protected void Page_Load(object sender, EventArgs e)
{
string format = Convert.ToString(ViewData["format"]);
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode("费用报销表", Encoding.UTF8) + string.Format(".{0}",format));
//测试中发现：如果要想在IE中直接打开PDF，上行代码，不能有！！否则即使客户端有设置，也会使用 Adobe Reader/Acrobat 打开
Response.ContentType = string.Format("application/{0}",format);
Response.Charset = "GB2312";
Response.ContentEncoding = System.Text.Encoding.UTF8;
Response.BinaryWrite(ViewData.Model);
Response.Flush();
//prevent render html to client(critical)
Response.End();
request to doc directly
Response.Redirect(“http://localhost:2222/Docs/abc.doc”, true);
Tips:
至于客户端使用浏览器打开(当然必须要相应的浏览器插件支持)，还是相应的application (MS-Word,Adobe Reader),打开前是否提示下载，Server端是无法控制的，这个和用户设置有关系。见图
webconfig伪静态
<system.web>
<httpHandlers>
<add verb="*" path="*.aspx" type="URLRewriter.RewriterFactoryHandler, URLRewriter"/>
<add verb="*" path="*.html" type="URLRewriter.RewriterFactoryHandler, URLRewriter"/>
</httpHandlers>
</system.web>
......
