如何在 dotnet core 的块 blob 类型存储中的现有文件中追加新的 csv 数据我尝试追加，但显示错误

如何解决如何在 dotnet core 的块 blob 类型存储中的现有文件中追加新的 csv 数据我尝试追加，但显示错误

这是我的代码：

CloudStorageAccount storageAccount = CloudStorageAccount.Parse(AzureWebJobsStorage);
CloudBlobClient serviceClient = storageAccount.CreateCloudBlobClient();
CloudBlobContainer container = serviceClient.GetContainerReference(ContainerName); 
// CloudBlobContainer containerbackup = serviceClient.GetContainerReference(ContainerNameBackup); 
CloudBlockBlob blob = container.GetBlockBlobReference(FileName);
// CloudBlockBlob blobBackUp = containerbackup.GetBlockBlobReference(FileName);
// CloudAppendBlob appendBlob = container.GetAppendBlobReference(FileName);
byte[] csvFile = Encoding.UTF8.GetBytes(csveventcontent.ToString().Trim());

if ( await blob.ExistsAsync())

    using (var appendFileStream = new MemoryStream(csvFile))
    await blob.UploadFromStreamAsync(appendFileStream);

else
{
    using (var uploadFileStream = new MemoryStream(csvFile))
    {
    await blob.UploadFromStreamAsync(uploadFileStream);
    uploadFileStream.Close();

    }  
}
       

解决方法

没有直接追加数据的方法。 UploadFromStreamAsync 用于将流上传到块 blob。如果 blob 已经存在，它将被覆盖。

您可以将 blob 文件作为流下载，然后附加 csv 数据流，最后上传新的流。

// download the blob stream:
MemoryStream stream = new MemoryStream();
await blob.DownloadToStreamAsync(stream);    
stream.Position = 0;

// append the stream,refer to https://stackoverflow.com/questions/15655210/how-to-merge-two-memory-streams
var newStream = Append(stream,appendFileStream);

// upload the new stream
await blob.UploadFromStreamAsync(newStream);

---

附加流方法：

public static Stream Append(Stream destination,Stream source)
{
    destination.Position = destination.Length;
    source.CopyTo(destination);
    destination.Position = 0;
    return destination;
}

---

我的测试代码：

class Program
{
    static async System.Threading.Tasks.Task Main(string[] args)
    {
        var StorageConnectionString = "";

        CloudStorageAccount storageAccount = CloudStorageAccount.Parse(StorageConnectionString);
        CloudBlobClient serviceClient = storageAccount.CreateCloudBlobClient();
        CloudBlobContainer container = serviceClient.GetContainerReference("pamelac");
        CloudBlockBlob blob = container.GetBlockBlobReference("test.txt");

        var appendFileStream = GetStreamFromString("hello"); // just for test,it will be "var appendFileStream = new MemoryStream(csvFile);" in your case

        // download the blob stream:
        MemoryStream stream = new MemoryStream();
        await blob.DownloadToStreamAsync(stream);
        stream.Position = 0;
        Console.WriteLine("download stream to string: \n" + Encoding.UTF8.GetString((stream as MemoryStream).ToArray()));

        // append the stream
        var newStream = Append(stream,appendFileStream);
        Console.WriteLine("new stream to string: \n" + Encoding.UTF8.GetString((newStream as MemoryStream).ToArray()));

        // upload the new stream
        await blob.UploadFromStreamAsync(newStream);

    }

    public static Stream GetStreamFromString(string text)
    {
        MemoryStream stream = new MemoryStream();
        StreamWriter writer = new StreamWriter(stream);
        writer.Write(text);
        writer.Flush();
        stream.Position = 0;

        return stream;
    }
    public static Stream Append(Stream destination,Stream source)
    {
        destination.Position = destination.Length;
        source.CopyTo(destination);
        destination.Position = 0;
        return destination;
    }
}