C# 文件操作(上传，下载，读取，写入)
1. 通过byte[]数据下载文件（这种方法可用于以开放Api的形式传递文件内容）
public void FileDownLoadByByte(byte[] fileData, string fileName)
{
//添加这个编码可以防止在IE下文件名乱码的问题
fileName = HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8);
Response.Clear();
Response.ClearHeaders();
Response.Buffer = true;
Response.ContentType = "application/octet-stream";
Response.AppendHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.AppendHeader("Content-Length", fileData.Length.ToString());
Response.BinaryWrite(fileData);
Response.Flush();
Response.End();
}
2. 根据路劲，从服务器下载文件
①
/// <summary> /// 从服务器下载文件 /// </summary> /// <param name="fileName">客户端保存的文件名</param> /// <param name="serverFilePath">服务器端要下载的文件路径</param> protected void LoadFileFromServer(string fileName, string serverFilePath) { FileInfo fileInfo = new FileInfo(serverFilePath); 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(); }
②
/// <summary> /// 微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite /// 下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。 /// 将后台文件写入 HTTP 响应输出流（不在内存中进行缓冲） /// </summary> public void TransmitFile() { Response.ContentType = "application/x-zip-compressed"; Response.AddHeader("Content-Disposition", "attachment;filename=download.zip"); string filename = Server.MapPath("~/Download/xx.zip"); Response.TransmitFile(filename); }
3. 通过流的形式下载文件
public void LoadFileByStream() { string fileName = "aaa.txt";//客户端保存的文件名 string filePath = Server.MapPath("~/Download/xx.txt"); //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(); }
4. Excel下载
参考另一篇博文
http://www.cnblogs.com/TiestoRay/archive/2013/02/02/2576134.html
5. 如果是用的.NET MVC3(及以上) 一切变得更加简单
例如
public ActionResult LoadFile2() { string filePath = Server.MapPath("~/Download/xx.jpg"); return File(filePath, "application/x-jpg", "demo.jpg"); }
它共有六种可用形式
FileContentResult File(byte[] fileContents, string contentType); FileStreamResult File(Stream fileStream, string contentType); FilePathResult File(string fileName, string contentType); virtual FileContentResult File(byte[] fileContents, string contentType, string fileDownloadName); virtual FileStreamResult File(Stream fileStream, string contentType, string fileDownloadName); virtual FilePathResult File(string fileName, string contentType, string fileDownloadName);
6. Ftp文件处理
参考 C#Ftp文件处理
7. 文件上传
将这种稍作修改即可解决跨域文件上传的问题，具体内容参考 跨域文件上传解决方案
后台代码
using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace SmsWebSystem.Upload { /// <summary> /// FileHandler 的摘要说明 /// </summary> public class FileHandler : IHttpHandler { private const int MAX_UPLOAD_SIZE = 2; /// <summary> /// fileSelector是前台代码中文件控件的name /// </summary> /// <param name="req"></param> /// <param name="res"></param> /// <returns></returns> public string UploadFile(HttpRequest req ,HttpResponse res) { if (req.Files["fileSelector"].ContentLength > MAX_UPLOAD_SIZE * 1024 * 1024) { return String.Format("请上传{0}M以内的文件。", MAX_UPLOAD_SIZE); } string uploadFileName = req.Files["fileSelector"].FileName; string path = HttpContext.Current.Server.MapPath(uploadFileName); req.Files["fileSelector"].SaveAs(path); return ""; } /// <summary> /// 需要指定上传结束后的回调函数 这里是uploadCallBack /// </summary> /// <param name="context"></param> public void ProcessRequest(HttpContext context) { string result = UploadFile(context.Request, context.Response); if (String.IsNullOrEmpty(result)) { result = "上传成功"; } context.Response.Write(String.Format("<script>top.uploadCallBack('{0}');</script>", result)); } public bool IsReusable { get { return false; } } } }
前台代码
<html xmlns="http://www.w3.org/1999/xhtml"> <body> <form id="fileform" name = "fileform" enctype="multipart/form-data" action="FileHandler.ashx" target="hideFrame" method="post"> <input type="file" id="fileSelector" name="fileSelector" /> </form> <iframe id="hideFrame" name="hideFrame" style="display:none;"></iframe> <input type="button" id="btnUpload" value="上传" /> </body> <script> document.querySelector("#btnUpload").onclick = function () { this.style.backgroundColor = "blue"; document.querySelector("#fileform").submit(); } function uploadCallBack(rst) { document.querySelector("#btnUpload").style.backgroundColor = "white"; alert(rst); } </script> </html>
8. 使用文件流写入文件数据
FileStream fs = new FileStream(FILE_PATH,FileMode.OpenOrCreate); string content = "";//要写入的内容 //获得字节数组 byte [] data =new UTF8Encoding().GetBytes(content); //开始写入，第二个参数用文件流的长度 表示向文件末尾追加内容 fs.Write(data,fs,data.Length); //清空缓冲区 fs.Flush(); //关闭流 fs.Close();
要注意的一点是，如果上传的文件过大，可能会报异常
【HTTP错误404.13 - Not Found 请求筛选模块被配置为拒绝超过请求内容长度的请求，原因是Web服务器上的请求筛选被配置为拒绝该请求，因为内容长度超过配置的值】
需要配置IIS配置文件（%windir%/system32/inetsrv/config/applicationhost.config）及项目配置文件 web.config
具体内容参考 《IIS请求筛选模块被配置为拒绝超过请求内容长度的请求》
9.使用文件流读取文件数据
byte[] byData = new byte[100]; //读取文件 FileStream fs = new FileStream(FILE_PATH,FileMode.Open); byte[] tmpData = new byte[fs.Length]; char[] charData = new char[fs.Length]; fs.Read(tmpData, 0, 100); //解码 Decoder d = Encoding.UTF8.GetDecoder(); d.GetChars(tmpData, 0, tmpData.Length, charData, 0); Console.WriteLine(charData);
接下来还有通过BufferedStream 读写文件的方式，未完待续
参考 https://msdn.microsoft.com/zh-cn/library/3dsccbf4(VS.80).aspx
