Response.ContentType = "application/x-zip-compressed";
Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
string filename = Server.MapPath("DownLoad/aaa.zip");
Response.TransmitFile(filename);
}

//WriteFile实现下载
protected void Button2_Click(object sender, EventArgs e)
{

string fileName ="aaa.zip";//客户端保存的文件名
string filePath=Server.MapPath("DownLoad/aaa.zip");//路径

FileInfo fileInfo = new FileInfo(filePath);
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.AddHeader("Content-Length", fileInfo.Length.ToString());
Response.AddHeader("Content-Transfer-Encoding", "binary");
Response.ContentType = "application/octet-stream";
Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
Response.WriteFile(fileInfo.FullName);
Response.Flush();
Response.End();
}

//WriteFile分块下载
protected void Button3_Click(object sender, EventArgs e)
{

string fileName = "aaa.zip";//客户端保存的文件名
string filePath = Server.MapPath("DownLoad/aaa.zip");//路径

System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

if (fileInfo.Exists == true)
{
const long ChunkSize = 102400;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力
byte[] buffer = new byte[ChunkSize];

Response.Clear();
System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
long dataLengthToRead = iStream.Length;//获取下载的文件总大小
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
while (dataLengthToRead > 0 && Response.IsClientConnected)
{
int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
Response.OutputStream.Write(buffer, 0, lengthRead);
Response.Flush();
dataLengthToRead = dataLengthToRead - lengthRead;
}
Response.Close();
}
}

//流方式下载
protected void Button4_Click(object sender, EventArgs e)
{
string fileName = "aaa.zip";//客户端保存的文件名
string filePath = Server.MapPath("DownLoad/aaa.zip");//路径

//以字符流的形式下载文件
FileStream fs = new FileStream(filePath, FileMode.Open);
byte[] bytes = new byte[(int)fs.Length];
fs.Read(bytes, 0, bytes.Length);
fs.Close();
Response.ContentType = "application/octet-stream";
//通知浏览器下载文件而不是打开
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
Response.BinaryWrite(bytes);
Response.Flush();
Response.End();

}