dotnetzip 创建空的损坏文件

Posted 2023-02-25

【中文标题】dotnetzip 创建空的损坏文件

【英文标题】：dotnetzip creating empty corrupted file

【发布时间】：2019-05-01 19:11:20

【问题描述】：

我正在尝试创建一个 HTTP 触发函数，该函数将从 Azure 存储中提取一个 blob，对其进行压缩，然后将 zip 重新上传到 blob 存储。在此过程中的某个地方出现了问题。它成功压缩并重新上传，但压缩文件的内容为 0KB，无法打开。任何帮助，将不胜感激。在下面找到代码。

 public static async Task<HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)]HttpRequestMessage req, TraceWriter log)
    
        log.Info("C# HTTP trigger function processed a request.");
        try
        
          string fileName = req.GetQueryNameValuePairs()
                .FirstOrDefault(q => string.Compare(q.Key, "fileName", true) == 0)
                .Value;

            log.Info($"fileName: fileName");

            dynamic request = await req.Content.ReadAsAsync<object>();
            var container = (string)request.body;

            string connectionString = Environment.GetEnvironmentVariable("blobstorageconnectionstring");
            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);
            CloudBlobClient client = storageAccount.CreateCloudBlobClient();

            MemoryStream outputStream = new MemoryStream();

            using (ZipFile zip = new ZipFile())
            
                zip.AddEntry($"fileName.xlsx", DownloadFromBlobStorage(fileName, connectionString, container));
                zip.CompressionMethod = CompressionMethod.Deflate;
                zip.Save(outputStream);
            


            UploadToBlobStorage(fileName + "ZIP", outputStream, connectionString, container);

            return req.CreateResponse(HttpStatusCode.OK, "OK");
        
        catch (Exception ex)
        
            log.Error("error", ex: ex);

            return req.CreateResponse(HttpStatusCode.BadRequest);
        

    
    private static void UploadToBlobStorage(string name, MemoryStream dataStream, string storageConnectionString, string blobContainerName)
    

        CloudStorageAccount account = CloudStorageAccount.Parse(storageConnectionString);
        CloudBlobClient client = account.CreateCloudBlobClient();

        CloudBlobContainer container = client.GetContainerReference(blobContainerName);
        container.CreateIfNotExists();

        CloudBlockBlob blob = container.GetBlockBlobReference(name);
        blob.Properties.ContentType = "application/x-zip-compressed";

        dataStream.Position = 0;
        blob.UploadFromStream(dataStream);
    
    private static MemoryStream DownloadFromBlobStorage(string fileName, string storageConnectionString, string blobContainerName)
    

        CloudStorageAccount account = CloudStorageAccount.Parse(storageConnectionString);
        CloudBlobClient client = account.CreateCloudBlobClient();

        CloudBlobContainer container = client.GetContainerReference(blobContainerName);
        container.CreateIfNotExists();

        CloudBlockBlob blob = container.GetBlockBlobReference(fileName);

        MemoryStream memStream = new MemoryStream();

        blob.DownloadToStream(memStream);

        return memStream;
    

【参考方案1】：

您似乎也应该将从DownloadFromBlobStorage() 返回的MemoryStream 对象定位为零（您已经在UploadToBlobStorage() 上使用outputStream/dataStream 执行此操作），然后将其传递给zip.AddEntry()：

   MemoryStream inputStream = DownloadFromBlobStorage(fileName, connectionString, container);
   inputStream.Position = 0;
   zip.AddEntry($"fileName.xlsx", inputStream);

看看这个答案：

Creating Zip file from stream and downloading it - Stack Overflow

经过更多研究，我发现通常您应该始终在将流传递给函数之前定位它：

Who is responsible for stream positioning? - Software Engineering Stack Exchange

【讨论】：

修复了它。我觉得很笨。谢谢！！

作为替代方案：inputStream.Seek(0, SeekOrigin.Begin);

@JohnyL，是的，这就是我链接的答案中使用它的方式，所以我研究了差异，但在这种情况下，两种方法之间没有区别：Stream.Seek(0, SeekOrigin.Begin) or Position = 0