将DataSet导出到客户端输出流中

方法1：
   // 创建MemeoryStream
   System.IO.MemoryStream ms = new System.IO.MemoryStream();
   // 写dataset到MemeoryStream
   ds.WriteXml(ms,XmlWriteMode.IgnoreSchema);
   Response.Clear();
   // 下载附件的名字
   Response.AddHeader("Content-Disposition", "attachment; filename=Acounts.xml");
   // 下载附件的大小，以便让浏览器显示进度条
   Response.AddHeader("Content-Length", ms.Length.ToString());
   // 指定浏览器为下载模式
   Response.ContentType = "application/octet-stream";
   // 发送到客户端
   byte[] b = ms.ToArray(); 
   Response.OutputStream.Write(b,0,b.Length);
   Response.End();
方法2：

XmlTextWriter writer = new XmlTextWriter(Response.OutputStream, Encoding.UTF8);　　
writer.Formatting = Formatting.Indented;　　
writer.Indentation = 4;　
writer.IndentChar = ' ';　
writer.WriteRaw("<?xml version=\"1.0\" ?>"); 

 ds.WriteXml(writer);
  
Response.AddHeader("Content-Disposition", "attachment; filename=Acounts.xml");
this.Response.ContentType = "text/xml";
Response.ContentType = "application/octet-stream";
writer.Flush();
Response.End();　　
writer.Close();　　

方法3：自定义一个XML文件输出

XmlTextWriter writer = new XmlTextWriter(Response.OutputStream, Encoding.UTF8);　　
   writer.Formatting = Formatting.Indented;　　
   writer.Indentation = 4;　
   writer.IndentChar = ' ';　
   writer.WriteRaw("<?xml version=\"1.0\" ?>"); 
   writer.WriteStartElement("Yuanlin");

   //writer.e
   for(int i=0;i<dt.Rows.Count;i++)
   {
    writer.WriteStartElement("Corp");
     writer.WriteAttributeString("id",dt.Rows.Count.ToString());
     writer.WriteStartElement("CorpInfo");
      writer.WriteElementString("Name",dt.Rows[i]["Name"].ToString());
      writer.WriteElementString("AptLevel",dt.Rows[i]["AptLevel"].ToString());
      writer.WriteElementString("CropBirthDate",dt.Rows[i]["CropBirthDate"].ToString());
      writer.WriteElementString("ManageDept",dt.Rows[i]["ManageDept"].ToString());
      writer.WriteElementString("Province",dt.Rows[i]["Province"].ToString());
      writer.WriteElementString("City",dt.Rows[i]["City"].ToString());
      writer.WriteElementString("Region",dt.Rows[i]["Region"].ToString());
      writer.WriteElementString("Address",dt.Rows[i]["Address"].ToString());
     writer.WriteEndElement();
     //获取人员信息
     DataView dv = DtEmployee.DefaultView;
     dv.RowFilter = String.Format("FBaseInfoID='{0}'",dt.Rows[i]["FID"].ToString());
     
     for(int j=0;j<dv.Count;j++)
     {
      writer.WriteStartElement("USerInfo");
      writer.WriteElementString("Name",dv[j].Row["Name"].ToString());
      writer.WriteElementString("Sex",dv[j].Row["Sex"].ToString());
      writer.WriteElementString("CardCode",dv[j].Row["CardCode"].ToString());
      writer.WriteElementString("Specialty",dv[j].Row["Specialty"].ToString());
      writer.WriteElementString("Duty",dv[j].Row["Duty"].ToString());
      writer.WriteEndElement();
     }
     dv = DtProject.DefaultView;
     dv.RowFilter = String.Format("FBaseInfoID='{0}'",dt.Rows[i]["FID"].ToString());
     for(int j=0;j<dv.Count;j++)
     {
      writer.WriteStartElement("ProjectInfo");
      writer.WriteElementString("FProjectName",dv[j].Row["FProjectName"].ToString());
      writer.WriteElementString("FProvince",dv[j].Row["FProvince"].ToString());
      writer.WriteElementString("FCity",dv[j].Row["FCity"].ToString());
      writer.WriteElementString("FRegion",dv[j].Row["FRegion"].ToString());
      writer.WriteElementString("FProjectType",dv[j].Row["FProjectType"].ToString());
      writer.WriteElementString("FArea",dv[j].Row["FArea"].ToString());
      writer.WriteElementString("FPrice",dv[j].Row["FPrice"].ToString());
      writer.WriteElementString("FCompleteArea",dv[j].Row["FCompleteArea"].ToString());
      writer.WriteElementString("FCompleteCost",dv[j].Row["FCompleteCost"].ToString());
      writer.WriteEndElement();
     }
     
    writer.WriteEndElement();
   }
   writer.WriteEndElement(); 
   Response.AddHeader("Content-Disposition", "attachment; filename=Acounts.xml");
   this.Response.ContentType = "text/xml";
   Response.ContentType = "application/octet-stream";
   writer.Flush();
   Response.End();　　
   writer.Close();