C#實現文件下載

1，Http 協議中有專門的指令來告知瀏覽器, 本次響應的是一個需要下載的文件. 格式如下:
Content-Disposition: attachment;filename=filename.ext
以上指令即標記此次響應流是附件,且附件文件名為 filename.ext
注意：
(1): 中文文件名需要進行URLEncode編碼, 否則在IE 6 下會提示是”無法識別的文件”.

但經實際測試,在Chrome下不進行URLEncode編碼, 也能正常顯示.

(2): 文件名不能有空格, 否則也會被認為是”無法識別的文件”.

(3): [ASP.Net中] 向響應流中添加該指令必須使用 response.AddHeader() 函數; 使用

response.Header.Add() 則會報錯.

下面是一個實現下載文件功能的函數：

/// <summary>
        /// 使用微軟的TransmitFile下載文件
        /// </summary>
        /// <param name="filePath">服務器相對路徑</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格式為壓縮包
                    HttpContext.Current.Response.ContentType = "application/x-zip-compressed";
                   
                     // Http 協議中有專門的指令來告知瀏覽器, 本次響應的是一個需要下載的文件. 格式如下:
                    // Content-Disposition: attachment;filename=filename.txt
                    HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode(info.FullName));
                    //不指明Content-Length用Flush的話不會顯示下載進度   
                    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();
            }

        }

2 下面是使用WriteFile實現下載

/// <summary>
        /// 使用WriteFile下載文件  
        /// </summary>
        /// <param name="filePath">相對路徑</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=" + Server.UrlEncode(info.FullName));
                    //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();
            }
        }

3，下面是分塊實現下載：

/// <summary>
        /// 使用OutputStream.Write分塊下載文件  
        /// </summary>
        /// <param name="filePath"></param>
        public void WriteFileBlock(string filePath)
        {
            filePath = Server.MapPath(filePath);
            if (!File.Exists(filePath))
            {
                return;
            }
            FileInfo info = new FileInfo(filePath);
            //指定塊大小   
            long chunkSize = 4096;
            //建立一個4K的緩沖區   
            byte[] buffer = new byte[chunkSize];
            //剩余的字節數   
            long dataToRead = 0;
            FileStream stream = null;
            try
            {
                //打開文件   
                stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
                
                dataToRead = stream.Length;

                //添加Http頭   
                HttpContext.Current.Response.ContentType = "application/octet-stream";
                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachement;filename=" + Server.UrlEncode(info.FullName));
                HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());

                while (dataToRead > 0)
                {
                    if (HttpContext.Current.Response.IsClientConnected)
                    {
                        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失去連接   
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                HttpContext.Current.Response.Write("Error:" + ex.Message);
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                }
                HttpContext.Current.Response.Close();
            }

        }

轉 https://www.cnblogs.com/wang7/archive/2012/08/07/2627298.html