Update stream-files-tutorial-with-api.md

Author: Juliako

articles/media-services/latest/stream-files-tutorial-with-api.md

@@ -84,6 +84,8 @@ The following function performs these actions:
 
 * Creates an **Asset**.
 * Gets a writable [SAS URL](https://docs.microsoft.com/azure/storage/common/storage-dotnet-shared-access-signature-part-1) to the asset’s [container in storage](https://docs.microsoft.com/azure/storage/blobs/storage-quickstart-blobs-dotnet#upload-blobs-to-a-container).
+
+    If using asset’s [ListContainerSas](https://docs.microsoft.com/rest/api/media/assets/listcontainersas) function to get SAS URLs, note that the function returns multiple SAS URLs as there are two storage account keys for each storage account. A storage account has two keys because it allows for seamless rotation  of storage account keys (for example, change one while using the other then start using the new key and rotate the other key). The 1st SAS URL represents storage key1 and second one storage key2.
 * Uploads the file into the container in storage using the SAS URL.
 
 [!code-csharp[Main](../../../media-services-v3-dotnet-tutorials/AMSV3Tutorials/UploadEncodeAndStreamFiles/Program.cs#CreateInputAsset)]