async await 异步下载 异步代码加锁 lock 异步缓存

    async await 异步下载 异步代码加锁 lock 异步缓存

    FTP异步下载代码：

/// <summary>
/// 异步下载文件
</summary>
<param name="ftpPath">ftp路径</param>
<param name="ftpUserId">用户名<param name="ftpPassword">密码<param name="relativeFilePath">文件相对路径</param>
public static async Task<MemoryStream> DownloadFileAsync(string ftpPath,string ftpUserId,1)">string ftpPassword,1)">string relativeFilePath)
{
    FtpWebRequest request = null;

    try
    {
        LogTimeUtil log = new LogTimeUtil();
        request = (FtpWebRequest)WebRequest.Create(new Uri(Path.Combine(ftpPath,relativeFilePath).Replace("\\",/")));
        request.Credentials =  NetworkCredential(ftpUserId,ftpPassword);
        request.Method = RETR;
        FtpWebResponse response = (FtpWebResponse)(await request.GetResponseAsync());
        Stream responseStream = response.GetResponseStream();
        MemoryStream stream =  MemoryStream();
        byte[] bArr = new byte[1024 * 1024];
        int size = await responseStream.ReadAsync(bArr,1)">0,(int)bArr.Length);
        while (size > 0)
        {
            stream.Write(bArr,,size);
            size = )bArr.Length);
        }
        stream.Seek(ftputil.DownloadFileAsync 下载 filePath=" + relativeFilePath);
        return stream;
    }
    catch (Exception ex)
    {
        request.Abort();
        LogUtil.Error(ex);
    }

    return ;
}

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    异步缓存代码：

 异步获取并缓存数据
<param name="cacheKey">键<param name="func">在此方法中初始化数据<param name="expirationSeconds">缓存过期时间(秒)，0表示永不过期<param name="refreshCache">立即刷新缓存async Task<T> TryGetValueAsync<T>(string cacheKey,Func<Task<T>> func,1)">int expirationSeconds = bool refreshCache = false)
{
    string pre = CacheHelper.TryGetValueAsync<T>;
    SemaphoreSlim sem = _dictSemaphoresForReadCache.GetorAdd(pre + cacheKey,1)">new SemaphoreSlim(1,1)">1));
     sem.WaitAsync();

    
    {
        object cacheValue = httpruntime.cache.Get(cacheKey);
        if (cacheValue != )
        {
             (T)cacheValue;
        }
        else
        {
            T value =  func();
            if (expirationSeconds > )
            {
                httpruntime.cache.Insert(cacheKey,value,Now.AddSeconds(expirationSeconds),Cache.NoSlidingExpiration);
            }
            
            {
                httpruntime.cache.Insert(cacheKey,value);
            }
             value;
        }
    }
     (Exception ex)
    {
        LogUtil.Error(ex);
        default(T);
    }
    finally
    {
        sem.Release();
    }
}

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    Web API 异步下载接口：

 文件下载
<param name="filePath">文件存储相对路径[HttpGet]
[Route(DownloadFileByPath)]
async Task<HttpResponseMessage> DownloadFileByPath( filePath)
{
    HttpResponseMessage response =  HttpResponseMessage();

     LogTimeUtil();
        string fileName = Path.GetFileName(filePath);

        if (ftputil.FileExists(_ftpPath,_ftpUserId,_ftpPassword,filePath))
        {
            await CacheHelper.TryGetValueAsync(DF9165DE189149258B34C405A2A7D7D1" + filePath,1)">async () =>
            {
                MemoryStream ms =  ftputil.DownloadFileAsync(_ftpPath,filePath);
                 ms.ToArray();
            },1)">180);

            response.Content =  ByteArrayContent(bArr);
            response.Content.Headers.ContentLength = bArr.Length;
            response.Content.Headers.Contentdisposition = new ContentdispositionHeaderValue(attachment);
            response.Content.Headers.Contentdisposition.FileName = fileName;
            response.Content.Headers.ContentType = new MediaTypeHeaderValue(application/octet-stream);
        }
        
        {
            LogUtil.Error(DownloadFileByPath 错误：文件不存在);
             HttpResponseMessage(HttpStatusCode.NotFound);
        }
        log.LogTime(CommonController.DownloadFileByPath 下载 filePath= filePath);
    }
     (Exception ex)
    {
        LogUtil.Error(ex,1)">DownloadFileByPath 错误);
         HttpResponseMessage(HttpStatusCode.NotFound);
    }

     response;
}

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