代碼如下:

using System; 
using System.Data; 
using System.Configuration; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Web.UI.HtmlControls; 
using System.IO; 
public partial class _Default : System.Web.UI.Page 
{ 
protected void Page_Load(object sender, EventArgs e) 
{ 
} 
//TransmitFile實現下載 
protected void Button1_Click(object sender, EventArgs e) 
{ 
Response.ContentType = "application/x-zip-compressed"; 
Response.AddHeader("Content-Disposition", "attachment;filename=z.zip"); 
string filename = Server.MapPath("DownLoad/z.zip"); 
Response.TransmitFile(filename); 
} 
//WriteFile實現下載 
protected void Button2_Click(object sender, EventArgs e) 
{ 
string fileName ="asd.txt";//客戶端保存的文件名 
string filePath=Server.MapPath("DownLoad/aaa.txt");//路徑 
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分塊下載 
protected void Button3_Click(object sender, EventArgs e) 
{ 
string fileName = "aaa.txt";//客戶端保存的文件名 
string filePath = Server.MapPath("DownLoad/aaa.txt");//路徑 
System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath); 
if (fileInfo.Exists == true) 
{ 
const long ChunkSize = 102400;//100K 每次讀取文件，只讀取100K，這樣可以緩解服務器的壓力 
byte[] buffer = new byte[ChunkSize]; 
Response.Clear(); 
System.IO.FileStream iStream = System.IO.File.OpenRead(filePath); 
long dataLengthToRead = iStream.Length;//獲取下載的文件總大小 
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));//讀取的大小 
Response.OutputStream.Write(buffer, 0, lengthRead); 
Response.Flush(); 
dataLengthToRead = dataLengthToRead - lengthRead; 
} 
Response.Close(); 
} 
} 
//流方式下載 
protected void Button4_Click(object sender, EventArgs e) 
{ 
string fileName = "aaa.txt";//客戶端保存的文件名 
string filePath = Server.MapPath("DownLoad/aaa.txt");//路徑 
//以字符流的形式下載文件 
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"; 
//通知瀏覽器下載文件而不是打開 
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8)); 
Response.BinaryWrite(bytes); 
Response.Flush(); 
Response.End(); 
} 
}