c#下载文件四种方法：
1. 流方式下载
2.TransmitFile实现下载
3.WriteFile实现下载
4.WriteFile分块下载
/// <summary>
/// 流方式下载文件不能超过400M
/// </summary>
/// <param name="filePath">服务器相对路径</param>
public void RenderToBrowser(string filePath)
{
filePath = Server.MapPath(filePath);//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";
//文件名+文件格式 （这里编码采用的是utf-8）
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode("文件名.txt", System.Text.Encoding.UTF8));
Response.BinaryWrite(bytes);
Response.Flush();
Response.End();
}
/// <summary>
/// TransmitFile下载文件
/// </summary>
/// <param name="filePath">服务器相对路径</param>
public void TransmitFile(string filePath)
{
try
{
filePath = Server.MapPath(filePath);
if (File.Exists(filePath))
{
FileInfo info = new FileInfo(filePath);
long fileSize = info.Length;
HttpContext.Current.Response.Clear();
//指定Http Mime格式为压缩包
HttpContext.Current.Response.ContentType = "application/x-zip-compressed";
// Http 协议中有专门的指令来告知浏览器, 本次响应的是一个需要下载的文件. 格式如下:
// Content-Disposition: attachment;filename=filename.txt
//客户端保存的文件名 info.Name(例如 aaa.txt) 编码格式为utf-8
HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(info.Name, System.Text.Encoding.UTF8));
//不指明Content-Length用Flush的话不会显示下载进度
HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString());
HttpContext.Current.Response.TransmitFile(filePath, 0, fileSize);
HttpContext.Current.Response.Flush();
}
}
catch
{ }
finally
{
HttpContext.Current.Response.Close();
}
}
/// <summary>
/// 使用WriteFile下载文件
/// </summary>
/// <param name="filePath">服务器相对路径</param>
public void WriteFile(string filePath)
{
try
{
filePath = Server.MapPath(filePath);
if (File.Exists(filePath))
{
FileInfo info = new FileInfo(filePath);
long fileSize = info.Length;
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.ContentType = "application/octet-stream";
HttpContext.Current.Response.AddHeader("Content-Disposition", "attachement;filename=" + HttpUtility.UrlEncode(info.Name, System.Text.Encoding.UTF8));
//指定文件大小
HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString());
HttpContext.Current.Response.WriteFile(filePath, 0, fileSize);
HttpContext.Current.Response.Flush();
}
}
catch
{ }
finally
{
HttpContext.Current.Response.Close();
}
}
/// <summary>
/// 使用OutputStream.Write分块下载文件
/// </summary>
/// <param name="filePath">服务器相对路径</param>
public void WriteFileBlock(string filePath)
{
filePath = Server.MapPath(filePath);
if (!File.Exists(filePath))
{
return;
}
FileInfo info = new FileInfo(filePath);
//指定块大小
long chunkSize = 4096;
//建立一个4K的缓冲区
byte[] buffer = new byte[chunkSize];
//剩余的字节数
long dataToRead = 0;
FileStream stream = null;
try
{
//打开文件
stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
dataToRead = stream.Length;
//添加Http头
HttpContext.Current.Response.ContentType = "application/octet-stream";
HttpContext.Current.Response.AddHeader("Content-Disposition", "attachement;filename=" + HttpUtility.UrlEncode(info.Name, System.Text.Encoding.UTF8));
HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());
while (dataToRead > 0)
{
if (HttpContext.Current.Response.IsClientConnected)
{
//public abstract int Read(byte[] buffer, int offset, int count)
//buffer缓冲区；offset:缓冲区存储数据的开始位置 count: 从流中最多读取的字节数
int length = stream.Read(buffer,0, Convert.ToInt32(chunkSize));
HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);
HttpContext.Current.Response.Flush();
HttpContext.Current.Response.Clear();
dataToRead -= length;
}
else
{
//防止client失去连接
dataToRead = -1;
}
}
}
catch (Exception ex)
{
HttpContext.Current.Response.Write("Error:" + ex.Message);
}
finally
{
if (stream != null)
{
stream.Close();
}
HttpContext.Current.Response.Close();
}
}