CloudBlob.BeginSetMetadata Method (BlobRequestOptions, AsyncCallback, Object)

private void Eg_BeginSetMetadata2(Uri blobEndpoint, string accountName, string accountKey)
{
    // Create a service client for credentialed access to the Blob service.
    CloudBlobClient blobClient =
        new CloudBlobClient(blobEndpoint,
            new StorageCredentialsAccountAndKey(accountName, accountKey));

    // Create a blob reference.
    CloudBlob myBlob = blobClient.GetBlobReference("mycontainer/myblob.txt");

    // Write text to the blob.
    myBlob.UploadText("One man that has a mind and knows it can always beat ten men who haven't and don't.");

    // Define metadata for the blob.
    myBlob.Metadata["category"] = "quotes";
    myBlob.Metadata["owner"] = "George Bernard Shaw";

    // Set options for the request. E.g., Specify an operation timeout of 20 seconds.
    BlobRequestOptions options = new BlobRequestOptions();
    options.Timeout = TimeSpan.FromSeconds(20.0);

    // At this point, myBlob still has no metadata.
    // Set the blob's metadata.
    // Use aResult to determine when this asynchronous call has completed.
    IAsyncResult aResult = myBlob.BeginSetMetadata(options, Eg_BeginSetMetadataCallback, myBlob);

    // The metatdata won't appear on the blob until the asynchronous call has completed.
    while (!aResult.IsCompleted)
    {
        // The calling thread can perfrom other work while the asynchronous call completes.
        Thread.Sleep(100);
    }

    // Verify that myBlob's metadata has been populated by enumerating it's metadata.
    foreach (var metadataKey in myBlob.Metadata.Keys)
    {
        Console.WriteLine("Metadata name:\t" + metadataKey.ToString());
        Console.WriteLine("Metadata value:\t" + myBlob.Metadata.Get(metadataKey.ToString()));
    }
}

private void Eg_BeginSetMetadataCallback(IAsyncResult result)
{
    CloudBlob blob = (CloudBlob)result.AsyncState;
    blob.EndSetMetadata(result);
}