一、文件下载（取消下载服务端不会知道）

	/// <summary>/// 文件下载/// </summary>/// <param name="FilePath">文件相对路径</param>/// <returns></returns>[HttpGet]public IActionResult DownloadFile([FromQuery] string FilePath){try{string filePath = GlobalConfig.Com.WebPath.UserResourcePath + FilePath;  //文件物理路径if (!System.IO.File.Exists(filePath)){LogHelper.Info($"客户端下载文件失败：文件不存在，文件绝对路径：{filePath}", LogHelper.GetCurSourceFileName(), LogHelper.GetLineNum());return new EmptyResult();}string fileName = Path.GetFileName(filePath);var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite, 4096, true);  //异步读取文件return File(fileStream, "application/octet-stream", fileName, true);  //为true时，支持断点续传}catch (Exception ex){LogHelper.Error("客户端下载文件出现异常：", ex, LogHelper.GetCurSourceFileName(), LogHelper.GetLineNum());return new EmptyResult();}}

二、.NET Core 写Response.Body下载（取消下载服务端知道）

	/// <summary>/// 文件中转下载/// </summary>/// <param name="FilePath">文件相对路径</param>/// <returns></returns>[HttpGet]public void DownloadFile1([FromQuery] string FilePath){try{string filePath = GlobalConfig.Com.WebPath.UserResourcePath + FilePath;  //文件物理路径if (!System.IO.File.Exists(filePath)){LogHelper.Info($"客户端下载文件失败：文件不存在，文件绝对路径：{filePath}", LogHelper.GetCurSourceFileName(), LogHelper.GetLineNum());return;}string fileName = Path.GetFileName(filePath);long beginPosition = 0;var fs = new FileStream(filePath, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite, 4096, true);//断点续传string rangeStr = Request.Headers["range"];  //range 参数格式：byte=1024-,这个是http协议的格式，也可以自定义格式if (!string.IsNullOrEmpty(rangeStr))  //断点续传{string byteStr = rangeStr.Split("=")?[1];if (!string.IsNullOrEmpty(byteStr)){var byteArr = byteStr.Split("-");if (byteArr != null && byteArr.Length > 1){beginPosition = Convert.ToInt64(byteArr[0]);}}}HttpContext.Response.ContentType = "application/octet-stream";HttpContext.Response.Headers.Append("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(fileName));HttpContext.Response.Headers.Append("Charset", "utf-8");HttpContext.Response.Headers.Append("Access-Control-Expose-Headers", "Content-Disposition");int bufferSize = 1024;  //每次读取1MB到服务器内存using (HttpContext.Response.Body){long contentLength = fs.Length;HttpContext.Response.ContentLength = contentLength;byte[] buffer;long hasRead = 0;while (hasRead < contentLength){if (HttpContext.RequestAborted.IsCancellationRequested){//取消下载会进来，这里可以做一些操作。。。。。break;}fs.Seek(hasRead, SeekOrigin.Begin);buffer = new byte[bufferSize];//从下载文件中读取bufferSize(1024字节)大小的内容到服务器内存中int currentRead = fs.Read(buffer, 0, bufferSize);HttpContext.Response.Body.WriteAsync(buffer, 0, currentRead);HttpContext.Response.Body.Flush();hasRead += currentRead;}if (hasRead == contentLength)  //下载完成{//下载完成之后要做的事。。。。return;}}}catch (Exception ex){LogHelper.Error("客户端下载文件出现异常：", ex, LogHelper.GetCurSourceFileName(), LogHelper.GetLineNum());return;}}