string xmlfilename = this.TextBox2.ToString();
        DataSet ds=(DataSet)Session["ds"];
        if(File.Exists(Server.MapPath(xmlfilename))!=true)
        {
            ds.WriteXml(Server.MapPath(xmlfilename));
            if(File.Exists(Server.MapPath(xmlfilename)))
            {
                Response.Write("转换成功");
                Button1.Enabled=false;
            }
        }
为什么这转换成的文件的名称不是我输入的名称了,变了System.Web.UI.WebControls.TextBox,为什么呢,求解!