GetBlobReferenceFromServer not working with relative URIs. Error: "Only absolute addresses are permitted"

Question

I am upgrading Azure Storage from 1.7 SDK to 2.3 SDK and have been updating my GetBlobReference(string) calls to GetBlockReferenceFromServer(Uri)

In the past I have been using relative URIs, but when I pass these through to GetBlockReferenceFromServer I get an error that says I cannot use absolute URIs (see stack below)

Sample code:

Dim myAccount As CloudStorageAccount = CloudStorageAccount.Parse(connectionString)
Dim myClient As CloudBlobClient = myAccount.CreateCloudBlobClient()
Dim myRelativeUri As New Uri("mycontainer/myblob.txt", UriKind.Relative)
Dim myBlobref As ICloudBlob = myClient.GetBlobReferenceFromServer(myRelativeUri) <- Errors on this line

Error stack:

System.ArgumentException: Address 'mycontainer/myblob.txt' is a relative address. Only absolute addresses are permitted.Parameter name: uri   
at Microsoft.WindowsAzure.Storage.StorageUri.AssertAbsoluteUri(Uri uri)   
at Microsoft.WindowsAzure.Storage.StorageUri.set_PrimaryUri(Uri value)   
at Microsoft.WindowsAzure.Storage.StorageUri..ctor(Uri primaryUri, Uri secondaryUri)   
at Microsoft.WindowsAzure.Storage.StorageUri..ctor(Uri primaryUri)   
at Microsoft.WindowsAzure.Storage.Blob.CloudBlobClient.GetBlobReferenceFromServer(Uri blobUri, AccessCondition accessCondition, BlobRequestOptions options, OperationContext operationContext)   at MySoftware.MyReference...

I don't understand why the Uri has to be absolute when the CloudBlobClient has a BaseUri to work from. Do I have to manually prepend the BaseUri on before I try to get the reference?

There is nothing in the technical reference about this.

Has anyone got relative URIs to work with GetBlobReferenceFromServer? Is there something that I am fundamentally doing wrong?

Answer 1

Thank you for your feedback. GetBlobReferenceFromServer requires absolute URIs, as it was designed for a specific scenario, where the user just has a URI to the blob and needs to get its blob type to even start working with it.

If you know the type of your blob, I would strongly recommend using GetContainerReference and then GetBlockBlobReference or GetPageBlobReference instead, as these methods do not have to make a call to the Azure Storage Service to get the blob type. Hence, they would reduce cost and increase performance. They also work directly with blob names, not URIs.