XmlWriter 表示一个编写器，该编写器提供一种快速、非缓存和只进的方式来生成包含 XML 数据的流或文件。这个就可以不占用内存，将数据放入磁盘中。也就不会出现内存溢出


public class FileExercise : System.Web.Services.WebService

    {

        [WebMethod]

        public void HelloWorld()

        {

            // 生成临时文件

            string tFName = System.IO.Path.GetTempFileName();//@"C:\ResponseStream.txt"

            System.IO.FileStream stream = System.IO.File.Open(tFName, System.IO.FileMode.OpenOrCreate, System.IO.FileAccess.ReadWrite);

            XmlWriter writer = XmlWriter.Create(stream);

            writer.WriteStartDocument();

            writer.WriteRaw("<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\">");

            writer.WriteRaw("<soap:Body>");

            writer.WriteStartElement(MethodInfo.GetCurrentMethod().Name + "Response", @"http://tempuri.org/");

            writer.Flush();

            // 返回的主体

            writer.WriteString("Hello word!");

            // 将内存缓冲数据写进磁盘 ，当数据量大的时候分批处理并及时写入磁盘，可以降低内存压力

            writer.Flush();

            writer.WriteEndElement();

            writer.WriteRaw("</soap:Body>");

            writer.WriteRaw("</soap:Envelope>");

            writer.WriteEndDocument();

            writer.Flush();

            writer.Close();

            stream.Close();

            HttpContext context = HttpContext.Current;

            //context.Response.ContentType = "application/soap+xml; charset=utf-8";

            context.Response.WriteFile(tFName);

            return;

        }

    }

}