问个导出到word的问题

private void ShowWord()
{

HttpContext.Current.Response.AppendHeader("Content-Disposition","attachment;filename=xx.doc"); 
HttpContext.Current.Response.Charset ="UTF-8";     
HttpContext.Current.Response.ContentEncoding =System.Text.Encoding.Default; 
HttpContext.Current.Response.ContentType ="application/ms-word ";
Page.EnableViewState =false;    
System.IO.StringWriter  tw = new System.IO.StringWriter() ; 
System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter (tw); 
this.Page.RenderControl(hw); 
HttpContext.Current.Response.Write(tw.ToString()); 
HttpContext.Current.Response.End(); 
}上面的方法是导出到word 应该怎么设置可以让文档打开的时候就进入页面模式而不是web模式呢？