private string GetBlobMD5(string containerName, string blobName)
{
var client = AzureHelper.GetCloudBlobClient();
var container = client.GetContainerReference(containerName);
var url = AzureHelper.GenerateUrl(containerName, blobName);
var blobRef = client.GetBlobReferenceFromServer(new Uri(url));
blobRef.FetchAttributes();
return blobRef.Properties.ContentMD5;
}