/// <summary>
/// This method copies the first incremental snapshot as a base blob in the target region
/// </summary>
/// <param name="backupStorageAccountBlobClient">An instance of BlobClient which represents the storage account where the base blob is stored.</param>
/// <param name="targetContainerName">The name of container in the target storage account where the base blob is stored</param>
/// <param name="targetBaseBlobName">The name of the base blob used for storing the backups in the target storage account </param>
/// <param name="sourceSnapshotSASUri">The SAS URI of the source snapshot</param>
/// <returns></returns>
private static async Task CopyFirstSnapshotToBackupStorageAccount(PageBlobClient targetBaseBlob, string sourceSnapshotSASUri)
{
PageBlobClient sourceSnapshot = new PageBlobClient(new Uri(sourceSnapshotSASUri));
//Get the size of the source snapshot
var snapshotProperties = await sourceSnapshot.GetPropertiesAsync();
long sourceSnapshotSize = snapshotProperties.Value.ContentLength;
//Create the target base blob with the same size as the source snapshot
await targetBaseBlob.CreateAsync(sourceSnapshotSize);
//Snapshots are stored as page blobs under the hood
//Get all the valid page ranges from the source snapshot.
//Learn more about page blobs and page ranges:
//https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blob-pageblob-overview
///https://blogs.msdn.microsoft.com/windowsazurestorage/2012/03/26/getting-the-page-ranges-of-a-large-page-blob-in-segments/
///https://docs.microsoft.com/en-us/rest/api/storageservices/get-page-ranges
PageRangesInfo pageRanges = await sourceSnapshot.GetPageRangesAsync();
await WritePageRanges(sourceSnapshotSASUri, targetBaseBlob, pageRanges);
await targetBaseBlob.CreateSnapshotAsync();
}
