OperationContext usage (Microsoft.WindowsAzure.Storage)

Question

I'm going to download blob from Azure Blob Storage to stream and I need to specify retry policy and timeouts. That's why I use the BlobRequestOptions (WindowsAzure.Storage NuGet package) instance to specify all these settings. I also want to use the asynchronous method DownloadToStreamAsync that needs some additional parameters to be passed (AccessCondition, OperationContext). My code:

var selfieBlob = new CloudBlockBlob(GetBlobUri(requestedUrl), _credentials);
await selfieBlob.DownloadToStreamAsync(
    targetStream,
    AccessCondition.GenerateEmptyCondition(),
    _blobOptions,
    new OperationContext());

Questions:

• Should I create a new instance of OperationContext each time?
• Why is it a required parameter for this method? Seems I don't understand why it's so necessary.

Answer 1

You can invoke the method DownloadToStreamAsync with default(OperationContext) . This is the same being done by other overloads of DownloadToStreamAsync . Check here

await selfieBlob.DownloadToStreamAsync(
    targetStream,
    default(AccessCondition),
    _blobOptions,
    default(OperationContext));

It's usually used for logging correlation. Check ExcecuteAsync method implementation here .

Answer 2

About the OperationContext parameter, @user1672994 's answer is right.

Refer to the CloudBlob.DownloadToStreamAsync Method's description , you could know why the parameter AccessCondition is required. You could set it to be null if you don't have the condition limitation.