C# 文件流下载相关整理
C# 流方式下载文件（hooyes提供）
private void Real(HttpResponse response, HttpRequest request)
{
if (File.Exists(request.PhysicalPath))
{
FileInfo file = new System.IO.FileInfo(request.PhysicalPath);
response.Clear();
response.AddHeader("Content-Disposition", "filename=" + file.Name);
response.AddHeader("Content-Length", file.Length.ToString());
string fileExtension = file.Extension.ToLower();
switch (fileExtension)
{
case ".mp3":
response.ContentType = "audio/mpeg3";
break;
case ".mpeg":
response.ContentType = "video/mpeg";
break;
case ".jpg":
response.ContentType = "image/jpeg";
break;
case ".bmp":
response.ContentType = "image/bmp";
break;
case ".gif":
response.ContentType = "image/gif";
break;
case ".doc":
response.ContentType = "application/msword";
break;
case ".css":
response.ContentType = "text/css";
break;
case ".html":
response.ContentType = "text/html";
break;
case ".htm":
response.ContentType = "text/html";
break;
case ".swf":
response.ContentType = "application/x-shockwave-flash";
break;
case ".exe":
response.ContentType = "application/octet-stream";
break;
case ".inf":
response.ContentType = "application/x-texinfo";
break;
default:
response.ContentType = "application/octet-stream";
break;
}
response.WriteFile(file.FullName);
response.End();
}
else
{
response.Write("File Not Exists");
}
}
}
写入后要判断文件是否存在，判断文件是否写入完成（是否被占用）
在程序中，我们经常遇到读写文件的情况,而这个时候该文件可能被其他程序占用，那么怎么判断文件是否被占用,从而友好的提示用户呢？
这里提供一个简单的办法,他就是尝试着去读该文件,如果失败，则说明文件被占用:
public static bool IsFileOpen(string filePath) { bool result = false; System.IO.FileStream fs=null; try { fs = File.OpenWrite(filePath); fs.Close(); } catch (Exception ex) { result = true; } return result;//true 打开 false 没有打开 }
MVC文件下载
public FileContentResult GetFile(int id) { SqlDataReader rdr; byte[] fileContent = null; string mimeType = "";string fileName = ""; const string connect = @"Server=.\SQLExpress;Database=FileTest;Trusted_Connection=True;"; using (var conn = new SqlConnection(connect)) { var qry = "SELECT FileContent, MimeType, FileName FROM FileStore WHERE ID = @ID"; var cmd = new SqlCommand(qry, conn); cmd.Parameters.AddWithValue("@ID", id); conn.Open(); rdr = cmd.ExecuteReader(); if (rdr.HasRows) { rdr.Read(); fileContent = (byte[])rdr["FileContent"]; mimeType = rdr["MimeType"].ToString(); fileName = rdr["FileName"].ToString(); } } return File(fileContent, mimeType, fileName); }
在View中最简单的使用来使用这个Action只需提供一个超链接：
<a href="/GetFile/1">Click to get file</a>
如果在数据库中存储的图片是图片类型，和使用超链接不同的是，我们通过指向Controller action的一个带有src属性的<image>标签来获取:
<img src="/GetFile/1" alt="My Image" />
下面再让我们来看看使用FilePathResult（用于从硬盘提取文件）是多简单的事：
public FilePathResult GetFileFromDisk() { string path = AppDomain.CurrentDomain.BaseDirectory + "uploads/"; string fileName = "test.txt"; return File(path + fileName, "text/plain", "test.txt"); }
而这也可以用过超链接提取:
<a href="/GetFileFromDisk">Click to get file</a>
而最后一个选择FileStreamResult也可以从磁盘中提取文件:
public FileStreamResult StreamFileFromDisk() { string path = AppDomain.CurrentDomain.BaseDirectory + "uploads/"; string fileName = "test.txt"; return File(new FileStream(path + fileName, FileMode.Open), "text/plain", fileName); }
FilePathResult和FileStreamResult的区别是什么？我们又该如何取舍呢？主要的区别是FilePathResult使用HttpResponse.TransmitFile来将文件写入Http输出流。这个方法并不会在服务器内存中进行缓冲，所以这对于发送大文件是一个不错的选择。他们的区别很像DataReader和DataSet的区别。于此同时， TransmitFile还有一个bug,这可能导致文件传到客户端一半就停了，甚至无法传送。而FileStreamResult在这方面就很棒了。比如说：返回Asp.net Chart 控件在内存中生成的图表图片，而这并不需要将图片存到磁盘中.
项目实例（生成pdf）
// 生成账单HTML页面
private string WriteHTMLFile(string strContent)
{
string createHtmlPath = System.Web.HttpContext.Current.Server.MapPath("/BillingFiles/DownloadFiles/");
Encoding code = Encoding.GetEncoding("utf-8");
// 读取模板文件
string templateHTML = System.Web.HttpContext.Current.Server.MapPath("/BillingFiles/Template/BillingTemplate.html");
StreamReader sr = null;
StreamWriter sw = null;
string str = string.Empty;
try
{
sr = new StreamReader(templateHTML, code);
str = sr.ReadToEnd();
}
catch (Exception ex)
{
log.Error("ReadFile Error:" + ex.Message + ex.InnerException + ex.StackTrace);
sr.Close();
return null;
}
string htmlFileName = "BillingDetail_" + currentUser.AccountId + DateTime.Now.ToString("_yyyyMMddHHmmss") + ".html";
str = str.Replace("{body}", strContent);
// 写HTML文件
try
{
sw = new StreamWriter(createHtmlPath + htmlFileName, false, code);
sw.Write(str);
sw.Flush();
}
catch (Exception ex)
{
log.Error("WriteFile Error:" + ex.Message + ex.InnerException + ex.StackTrace);
sw.Close();
return null;
}
finally
{
sw.Close();
}
log.Info("Create HTML ok acctid:" + currentUser.AccountId + " FILE:" + createHtmlPath + htmlFileName);
return createHtmlPath + htmlFileName;
}
private string CreateBillingPDF(string htmlPath)
{
// 从html路径中计算生成pdf的文件名
int begin = htmlPath.IndexOf("DownloadFiles");
int end = htmlPath.IndexOf(".html");
string pdfFileName = htmlPath.Substring(begin + 14, end - begin - 14) + ".pdf";
try
{
if (string.IsNullOrEmpty(htmlPath))
return null;
string pdfPath = System.Web.HttpContext.Current.Server.MapPath("/BillingFiles/DownloadFiles/") + pdfFileName;
Process p = new Process();
string str = System.Web.HttpContext.Current.Server.MapPath("/BillingFiles/wkhtmltopdf-0.8.3.exe");
if (!System.IO.File.Exists(str))
return null;
p.StartInfo.FileName = str;
p.StartInfo.Arguments = " \"" + htmlPath + "\" " + pdfPath;
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardInput = true;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.RedirectStandardError = true;
p.StartInfo.CreateNoWindow = true;
p.Start();
// 判断文件是否已经生成并且pdf写入完毕
bool b = true;
while (b)
{
if (System.IO.File.Exists(pdfPath))
{
if (IsFileOpen(pdfPath))
{
System.Threading.Thread.Sleep(500);
}
else
{
b = false;
}
}
else
{
System.Threading.Thread.Sleep(500);
}
}
string fileURL = String.Format("http://{0}{1}", Request.Url.Authority, Request.ApplicationPath) + "BillingFiles/DownloadFiles/" + pdfFileName;
log.Info("Create PDF ok acctid:" + currentUser.AccountId + " FILE:" + fileURL + " " + pdfPath);
return fileURL;
}
catch (Exception ex)
{
log.Error("CreatePDF Error: Acctid:" + currentUser.AccountId + ex.Message + ex.InnerException + ex.StackTrace);
}
return null;
}