Azure Storage Search Blobs by Metadata - azure

Question

I have CloudBlockBlobs that have metadata.
CloudBlockBlob blockBlob = container.GetBlockBlobReference("myblob.jpg");
using (var fileStream = System.IO.File.OpenRead(filePath))
{
blockBlob.UploadFromStream(fileStream);
blockBlob.Properties.ContentType = "image/jpg";
blockBlob.Metadata.Add("Title", "Yellow Pear");
blockBlob.SetProperties();
}
I see the Metadata is there:
Debug.WriteLine(blockBlob.Metadata["Title"]);
Now later if I query from storage I see the blobs but the Metadata is missing:
(in the below I know blobItems[0] had Metadata when uploaded but now blobItems[0].Metadata.Count == 0)
var blobItems = container.ListBlobs(
null, false, BlobListingDetails.Metadata);
I also noticed the Metadata is not available when I obtain the blob by itself:
CloudBlockBlob a = container.GetBlockBlobReference("myblob.jpg");
//Below throws an exception
var b = a.Metadata["Title"];
Thank you!

Answer 1

There are some issues with your code :(.
The blob doesn't have any metadata set actually. After setting the metadata, you're calling blob.SetProperties() method which only sets the blob's properties (ContentType in your example). To set the metadata, you would actually need to call blob.SetMetadata() method.
Your upload code is currently making 2 calls to storage service: 1) upload blob and 2) set properties. If you call SetMetadata then it would be 3 calls. IMHO, these can be combined in just 1 call to storage service by doing something like below:
using (var fileStream = System.IO.File.OpenRead(filePath))
{
blockBlob.Properties.ContentType = "image/jpg";
blockBlob.Metadata.Add("Title", "Yellow Pear");
blockBlob.UploadFromStream(fileStream);
}
This will not only upload the blob but also set it's properties and metadata in a single call to storage service.
Regarding
I also noticed the Metadata is not available when I obtain the blob by
itself:
CloudBlockBlob a = container.GetBlockBlobReference("myblob.jpg");
//Below throws an exception
var b = a.Metadata["Title"];
Basically the code above is just creating an instance of the blob on the client side. It doesn't actually fetch the properties (and metadata) of the blob. To fetch details about the blob, you would need to call FetchAttributes method on the blob. Something like:
CloudBlockBlob a = container.GetBlockBlobReference("myblob.jpg");
a.FetchAttributes();
If after that you retrieve blob's metadata, you should be able to see it (provided metadata was created properly).