azure - Request.Content.ReadAsMultipartAsync 引发 System.IO 异常

Question

我正在将图像上传到 ASP WebAPI 服务，然后将其上传到 windows azure。一切都工作得很好，但突然我开始遇到以下异常:

        System.IO.IOException: The process cannot access the file
        'C:\DWASFiles\Sites\Tasteat\Temp\BodyPart_a5c79910-6077-4c24-b814-10fdc0e0b3d4' 
        because it is being used by another process.

这是抛出异常的代码:

    var provider = new BlobStorageProvider(container);
    Trace.TraceInformation("Uploading raw image to blob");
    await Request.Content.ReadAsMultipartAsync(provider);
    Trace.TraceInformation("Uploading finished");

我知道它是这一行 await Request.Content.ReadAsMultipartAsync(provider); 因为我在日志中看到了它前面的行，但没有看到它后面的行。

有什么想法吗？

几天前一切都运转良好

Answer 1

看来我上面发布的代码实际上保存了本地文件，然后才将其上传到服务器，这会导致错误，但速度也很慢。经过多次尝试，我终于更改为以下解决方案，一切开始工作，而且速度更快!

首先创建一个streamprovider:

public class BlobStorageMultipartStreamProvider : MultipartStreamProvider
    {
        private readonly string _containerName;
        private readonly string _fileName;

        public BlobStorageMultipartStreamProvider(string containerName, string fileName)
        {
            _containerName = containerName;
            _fileName = fileName;
        }

        public override Stream GetStream(HttpContent parent, HttpContentHeaders headers)
        {
            Stream stream = null;

            if (!String.IsNullOrWhiteSpace(_fileName))
                {
                    string connectionString = ConfigurationManager.ConnectionStrings["BlobStorage"].ConnectionString;
                    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);
                    CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
                    CloudBlobContainer blobContainer = blobClient.GetContainerReference(_containerName);
                    CloudBlockBlob blob = blobContainer.GetBlockBlobReference(_fileName);
                    stream = blob.OpenWrite();
                }
            return stream;
        }
    }

上传代码:

 string fileName = Guid.NewGuid()+".Png";
                MultipartStreamProvider provider = new BlobStorageMultipartStreamProvider("container",fileName);
                Trace.TraceInformation("Uploading raw image to blob");                
                await Request.Content.ReadAsMultipartAsync(provider);
                Trace.TraceInformation("Uploading finished");