public override void Write(byte[] buffer, int offset, int count) {if (!_isOpen) __Error.StreamIsClosed();if (!_writable) __Error.WriteNotSupported();if (buffer==null)throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));if (offset < 0)throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));if (count < 0)throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));if (buffer.Length - offset < count)throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));int i = _position + count;// Check for overflowif (i < 0)throw new IOException(Environment.GetResourceString("IO.IO_StreamTooLong"));if (i > _length) {bool mustZero = _position > _length;if (i > _capacity) {bool allocatedNewArray = EnsureCapacity(i);if (allocatedNewArray)mustZero = false;}if (mustZero)Array.Clear(_buffer, _length, i - _length);_length = i;}if (count <= 8){int byteCount = count;while (--byteCount >= 0)_buffer[_position + byteCount] = buffer[offset + byteCount];}elseBuffer.InternalBlockCopy(buffer, offset, _buffer, _position, count);_position = i;return;}

         //测试byte数组 假设该数组容量是256Mbyte[] testBytes=new byte[256*1024*1024];MemoryStream ms = new MemoryStream();using (ms){for (int i = 0; i < 1000; i++){try{ms.Write(testBytes, 0, testBytes.Length);}catch{Console.WriteLine("该内存流已经使用了{0}M容量的内存,该内存流最大容量为{1}M,溢出时容量为{2}M", GC.GetTotalMemory(false) / (1024 * 1024),//MemoryStream已经消耗内存量ms.Capacity / (1024 * 1024), //MemoryStream最大的可用容量ms.Length / (1024 * 1024));//MemoryStream当前流的长度（容量）break;}}}Console.ReadLine();

        /// <summary>/// 演示在xmlWriter中使用MemoryStream/// </summary>public static void UseMemoryStreamInXMLWriter(){MemoryStream ms = new MemoryStream();using (ms){//定义一个XMLWriterusing (XmlWriter writer = XmlWriter.Create(ms)){//写入xml头writer.WriteStartDocument(true);//写入一个元素writer.WriteStartElement("Content");//为这个元素新增一个test属性writer.WriteStartAttribute("test");//设置test属性的值writer.WriteValue("逆时针的风");//释放缓冲，这里可以不用释放，但是在实际项目中可能要考虑部分释放对性能带来的提升writer.Flush();Console.WriteLine("此时内存使用量为:{2}KB,该MemoryStream的已经使用的容量为{0}byte,默认容量为{1}byte",Math.Round((double)ms.Length, 4), ms.Capacity,GC.GetTotalMemory(false)/1024);Console.WriteLine("重新定位前MemoryStream所在的位置是{0}",ms.Position);//将流中所在的当前位置往后移动7位，相当于空格ms.Seek(7, SeekOrigin.Current);Console.WriteLine("重新定位后MemoryStream所在的位置是{0}", ms.Position);//如果将流所在的位置设置为如下所示的位置则xml文件会被打乱//ms.Position = 0;writer.WriteStartElement("Content2");writer.WriteStartAttribute("testInner");writer.WriteValue("逆时针的风Inner");writer.WriteEndElement();writer.WriteEndElement();//再次释放writer.Flush();Console.WriteLine("此时内存使用量为:{2}KB,该MemoryStream的已经使用的容量为{0}byte,默认容量为{1}byte",Math.Round((double)ms.Length, 4), ms.Capacity, GC.GetTotalMemory(false)/1024);//建立一个FileStream  文件创建目的地是d:\test.xmlFileStream fs = new FileStream(@"d:\test.xml",FileMode.OpenOrCreate);using (fs){//将内存流注入FileStreamms.WriteTo(fs);if(ms.CanWrite)//释放缓冲区fs.Flush();}}}}

  public class ImageHandler : IHttpHandler{#region IHttpHandler Memberspublic bool IsReusable{get { return true; }}/// <summary>/// 实现IHTTPHandler后必须实现的方法/// </summary>/// <param name="context">HttpContext上下文</param>public void ProcessRequest(HttpContext context){context.Response.Clear();//得到图片名var imageName = context.Request["ImageName"] == null ? "逆时针的风": context.Request["ImageName"].ToString();//得到图片ID,这里只是演示，实际项目中不是这么做的var id = context.Request["Id"] == null ? "01": context.Request["Id"].ToString();//得到图片地址var stringFilePath = context.Server.MapPath(string.Format("~/Image/{0}{1}.jpg", imageName, id));//声明一个FileStream用来将图片暂时放入流中FileStream stream = new FileStream(stringFilePath, FileMode.Open);using (stream){//透过GetImageFromStream方法将图片放入byte数组中byte[] imageBytes = this.GetImageFromStream(stream,context);//上下文确定写到客户短时的文件类型context.Response.ContentType = "image/jpeg";//上下文将imageBytes中的数据写到前段context.Response.BinaryWrite(imageBytes);stream.Close();}}/// <summary>/// 将流中的图片信息放入byte数组后返回该数组/// </summary>/// <param name="stream">文件流</param>/// <param name="context">上下文</param>/// <returns></returns>private byte[] GetImageFromStream(FileStream stream, HttpContext context){//通过stream得到ImageImage image = Image.FromStream(stream);//加上水印image = SetWaterImage(image, context);//得到一个ms对象MemoryStream ms = new MemoryStream();using (ms){//将图片保存至内存流image.Save(ms, ImageFormat.Jpeg);byte[] imageBytes = new byte[ms.Length];ms.Position = 0;//通过内存流读取到imageBytesms.Read(imageBytes, 0, imageBytes.Length);ms.Close();//返回imageBytesreturn imageBytes;}}/// <summary>/// 为图片加上水印，这个方法不用在意，只是演示，所以没加透明度/// 下次再加上吧/// </summary>/// <param name="image">需要加水印的图片</param>/// <param name="context">上下文</param>/// <returns></returns>private Image SetWaterImage(Image image,HttpContext context) {Graphics graphics = Graphics.FromImage(image);Image waterImage = Image.FromFile(context.Server.MapPath("~/Image/逆时针的风01.jpg"));//在大图右下角画上水印图就行graphics.DrawImage(waterImage,new Point { X = image.Size.Width - waterImage.Size.Width,Y = image.Size.Height - waterImage.Size.Height });return image;}#endregion}

    <httpHandlers><add type="ImageHandler.ImageHandler,ImageHandler"  verb="*" path="ImageHandler.apsx"/></httpHandlers>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"><h2>About</h2><p>Put content here.<asp:Image runat="server" ImageUrl="ImageHandler.apsx?ImageName=逆时针的风&Id=02" /></p>
</asp:Content>