将文件即时上传到 Azure Blob

Question

我正在尝试创建一个文件并使用 CloudBlockBlob.UploadFromStreamAsync() 方法将其放入 blob 中。

代码如下：

    private async void CreateCsvFile(int recId)
    {
        using (var csvFile = new StreamWriter())
        {
            for (int i = 1; i <= recId; ++i)
            {
                Ad ad = db.Ads.Find(i);
                if (ad != null)
                {
                    string rec = String.Format("{0}, {1}, {2}, {3}, {4}", ad.Title, ad.Category, ad.Price, ad.Description, ad.Phone);
                    csvFile.WriteLine(rec);
                }
            }

            csvFile.Flush();
            string blobName = Guid.NewGuid().ToString() + recId.ToString() + ".csv";
            CloudBlockBlob fileBlob = fileBlobContainer.GetBlockBlobReference(blobName);
            await fileBlob.UploadFromStreamAsync((Stream) csvFile);
        }
    }

更新了新要求：

// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

// Create the streams used for encryption. 
using (MemoryStream msEncrypt = new MemoryStream())
{
   using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
   {
       using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
       {
           //Write all data to the stream.
           swEncrypt.Write(plainText);
       }
       encrypted = msEncrypt.ToArray();
   }
}

问题：

文件是即时创建的，而不是从客户端上传的。这是正确的做法吗？
编译器抱怨 2 个问题：1) StreamWriter 的 Ctor 不带 0 个参数； 2）类型'StreamWriter'无法转换为'Stream'（我在这里转换是因为UploadFromStreamAsync()方法将Stream类型作为参数）。如何修复编译器错误？谢谢！

Answer 1

所以我之前有一个到 blob 的流，如下所示：

public async Task<Stream> GetWriteStreamAsync(string storagePath, string contentType)
{
    var blockBlob = blobContainer.GetBlockBlobReference(storagePath);
    blockBlob.Properties.ContentType = contentType;
    CloudBlobStream bb = await blockBlob.OpenWriteAsync();
    return bb;
}

所以现在你可以

using(var str = await GetWriteStreamAsync("someBlobName.csv", "text/csv"))
using(var csvFile = new StreamWriter(str))
{
    for (int i = 1; i <= recId; ++i)
    {
        Ad ad = db.Ads.Find(i);
        if (ad != null)
        {
            string rec = String.Format("{0}, {1}, {2}, {3}, {4}", 
                                       ad.Title, 
                                       ad.Category, 
                                       ad.Price, 
                                       ad.Description, 
                                       ad.Phone);
            csvFile.WriteLine(rec);
        }
    }
    csvFile.Flush();
}

将文件即时上传到 Azure Blob

Uploading a file to Azure Blob on the fly

c#

azure-blob-storage