gistfile1.cs

public async Task Execute(Guid user, byte[] data)
{
    var account = new CloudStorageAccount(GetStorageCredentials(), true);
    var client = account.CreateCloudBlobClient();
    var container = client.GetContainerReference(Consts.MemberImageContainer);
    var block = container.GetBlockBlobReference(user.ToString("N") + ".jpg");

    using (var stream = new MemoryStream(data))
    {
        await Task.Factory.FromAsync(block.BeginUploadFromStream, block.EndUploadFromStream, stream, null);
    }
}

// or

public Task Execute(Guid user, byte[] data)
{
    var account = new CloudStorageAccount(GetStorageCredentials(), true);
    var client = account.CreateCloudBlobClient();
    var container = client.GetContainerReference(Consts.MemberImageContainer);
    var block = container.GetBlockBlobReference(user.ToString("N") + ".jpg");

    using (var stream = new MemoryStream(data))
    {
        return Task.Factory.FromAsync(block.BeginUploadFromStream, block.EndUploadFromStream, stream, null);
    }
}