当前位置：首页 > news >正文

C# 以文件流的形式返回本地文件或远程文件

news 2025/10/10 21:03:28

FileStream和FileInfo只能处理本地文件路径，无法直接处理HTTP URL。以下是几种实现远程PDF返回给前端的解决方案：

方案1：使用HttpClient下载远程文件（推荐）

[HttpGet]
public async Task<HttpResponseMessage> GetReportFile()
{  try{string orderNo = HttpContext.Current.Request.QueryString["orderNo"];string filePath = "D:\\1.pdf";if(!string.IsNullOrEmpty(orderNo)){            filePath = "http://www.a.com/1.pdf";// 使用HttpClient下载远程文件using (var httpClient = new HttpClient()){// 设置超时时间httpClient.Timeout = TimeSpan.FromSeconds(30);// 下载文件内容var response = await httpClient.GetAsync(filePath);response.EnsureSuccessStatusCode();var content = await response.Content.ReadAsByteArrayAsync();// 创建返回结果var result = new HttpResponseMessage(HttpStatusCode.OK);result.Content = new ByteArrayContent(content);result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("inline"){FileName = "document.pdf"};return result;}}else{// 处理本地文件FileInfo foundFileInfo = new FileInfo(filePath);FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);var result = new HttpResponseMessage(HttpStatusCode.OK);result.Content = new StreamContent(fs);result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("inline"){FileName = foundFileInfo.Name};return result;}}catch (Exception ex){logger.Error(ex, ex.Message);return new HttpResponseMessage(HttpStatusCode.BadRequest);}
}

方案2：流式传输（节省内存）【推荐】

[HttpGet]
public async Task<HttpResponseMessage> GetReportFile()
{  try{string orderNo = HttpContext.Current.Request.QueryString["orderNo"];string filePath = "D:\\1.pdf";if(!string.IsNullOrEmpty(orderNo)){            filePath = "http://www.a.com/1.pdf";using (var httpClient = new HttpClient()){httpClient.Timeout = TimeSpan.FromSeconds(30);// 流式下载var response = await httpClient.GetAsync(filePath, HttpCompletionOption.ResponseHeadersRead);response.EnsureSuccessStatusCode();var stream = await response.Content.ReadAsStreamAsync();var result = new HttpResponseMessage(HttpStatusCode.OK);result.Content = new StreamContent(stream);result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("inline"){FileName = "document.pdf"};return result;}}else{// 本地文件处理...}}catch (Exception ex){logger.Error(ex, ex.Message);return new HttpResponseMessage(HttpStatusCode.BadRequest);}
}

方案3：添加缓存和错误处理

[HttpGet]
public async Task<HttpResponseMessage> GetReportFile()
{  try{string orderNo = HttpContext.Current.Request.QueryString["orderNo"];string filePath = "D:\\1.pdf";if(!string.IsNullOrEmpty(orderNo)){            filePath = "http://www.a.com/1.pdf";using (var httpClient = new HttpClient()){// 添加User-Agent头，有些服务器需要httpClient.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0");httpClient.Timeout = TimeSpan.FromSeconds(30);// 先获取头部信息检查文件是否存在var headResponse = await httpClient.SendAsync(new HttpRequestMessage(HttpMethod.Head, filePath));if (!headResponse.IsSuccessStatusCode){return new HttpResponseMessage(HttpStatusCode.NotFound){Content = new StringContent("远程文件未找到")};}// 获取文件名（从Content-Disposition或URL中提取）string fileName = "document.pdf";if (headResponse.Content.Headers.ContentDisposition != null){fileName = headResponse.Content.Headers.ContentDisposition.FileName ?? fileName;}// 下载文件var getResponse = await httpClient.GetAsync(filePath, HttpCompletionOption.ResponseHeadersRead);getResponse.EnsureSuccessStatusCode();var result = new HttpResponseMessage(HttpStatusCode.OK);result.Content = new StreamContent(await getResponse.Content.ReadAsStreamAsync());result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("inline"){FileName = fileName};// 添加缓存头（可选）result.Headers.CacheControl = new CacheControlHeaderValue(){MaxAge = TimeSpan.FromHours(1)};return result;}}else{// 本地文件处理...}}catch (HttpRequestException httpEx){logger.Error(httpEx, "网络请求错误");return new HttpResponseMessage(HttpStatusCode.BadGateway);}catch (TaskCanceledException timeoutEx){logger.Error(timeoutEx, "请求超时");return new HttpResponseMessage(HttpStatusCode.RequestTimeout);}catch (Exception ex){logger.Error(ex, ex.Message);return new HttpResponseMessage(HttpStatusCode.InternalServerError);}
}