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C#實(shí)現(xiàn)以文件流的形式返回本地文件或遠(yuǎn)程文件路徑

更新時(shí)間：2025年08月21日 15:49:43 作者：VipSoft

FileStream和FileInfo只能處理本地文件路徑,無(wú)法直接處理HTTP URL,所以下面小編就來(lái)和大家詳細(xì)介紹一下C#如何實(shí)現(xiàn)以文件流的形式返回本地文件或遠(yuǎn)程文件路徑吧

方案1：使用HttpClient下載遠(yuǎn)程文件（推薦）

[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下載遠(yuǎn)程文件
            using (var httpClient = new HttpClient())
            {
                // 設(shè)置超時(shí)時(shí)間
                httpClient.Timeout = TimeSpan.FromSeconds(30);
                
                // 下載文件內(nèi)容
                var response = await httpClient.GetAsync(filePath);
                response.EnsureSuccessStatusCode();
                
                var content = await response.Content.ReadAsByteArrayAsync();
                
                // 創(chuàng)建返回結(jié)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
        {
            // 處理本地文件
            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：流式傳輸（節(jié)省內(nèi)存）【推薦】

[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);
                
                // 流式下載
                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
        {
            // 本地文件處理...
        }
    }
    catch (Exception ex)
    {
        logger.Error(ex, ex.Message);
        return new HttpResponseMessage(HttpStatusCode.BadRequest);
    }
}

方案3：添加緩存和錯(cuò)誤處理

[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頭，有些服務(wù)器需要
                httpClient.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0");
                httpClient.Timeout = TimeSpan.FromSeconds(30);
                
                // 先獲取頭部信息檢查文件是否存在
                var headResponse = await httpClient.SendAsync(new HttpRequestMessage(HttpMethod.Head, filePath));
                
                if (!headResponse.IsSuccessStatusCode)
                {
                    return new HttpResponseMessage(HttpStatusCode.NotFound)
                    {
                        Content = new StringContent("遠(yuǎn)程文件未找到")
                    };
                }
                
                // 獲取文件名（從Content-Disposition或URL中提?。?
                string fileName = "document.pdf";
                if (headResponse.Content.Headers.ContentDisposition != null)
                {
                    fileName = headResponse.Content.Headers.ContentDisposition.FileName ?? fileName;
                }
                
                // 下載文件
                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
                };
                
                // 添加緩存頭（可選）
                result.Headers.CacheControl = new CacheControlHeaderValue()
                {
                    MaxAge = TimeSpan.FromHours(1)
                };
                
                return result;
            }
        }
        else
        {
            // 本地文件處理...
        }
    }
    catch (HttpRequestException httpEx)
    {
        logger.Error(httpEx, "網(wǎng)絡(luò)請(qǐng)求錯(cuò)誤");
        return new HttpResponseMessage(HttpStatusCode.BadGateway);
    }
    catch (TaskCanceledException timeoutEx)
    {
        logger.Error(timeoutEx, "請(qǐng)求超時(shí)");
        return new HttpResponseMessage(HttpStatusCode.RequestTimeout);
    }
    catch (Exception ex)
    {
        logger.Error(ex, ex.Message);
        return new HttpResponseMessage(HttpStatusCode.InternalServerError);
    }
}