获取Azure Blob存储中的最后一个Blob

Question

I need to know how I can retrieve the last created blob in my blob storage. Now I'm doing it with a for loop, but there are approximately 50000 blockblobs in the directory.

How can I get the last created block blob on a efficient way?

My code is as follows:

string url = null;
foreach (var blobItem in subdir.ListBlobs())
{
    url = blobItem.Uri.ToString();
}
url += signature;
if (url != pictureBoxLiveViewer.ImageLocation)
{
    pictureBoxLiveViewer.ImageLocation = url;
}

This is a function in a timer who's ticking every minute. So this is inefficient.

Answer 1

Blob storage does not support querying capability so you would need to implement this on your own. One obvious option is the way you're currently doing it where you list the blobs and find the last blob in that list.

[Thinking out loud]

One thing you could do is name the blobs in reverse chronological order (approach similar to PartitionKey in tables). So what you could do is name your blob using this logic

var blobName = DateTime.MaxValue - DateTime.UtcNow

That way when you list the blob, you'll always get the latest blob first.

Another alternative could be to save the blob name, the creation date, and the blob URI in Table storage. Again, you may want to use the same logic as above for PartitionKey. Then you would query the table storage, get the 1st record from the table and that would be your most recently created blob.

Answer 2

I have created a function in my upload application that will write every time the full URI of the newest image in a text file (txt)

CloudBlobClient blobClient = new CloudBlobClient(
    sUrl, new StorageCredentialsSharedAccessSignature(signature));
CloudBlobContainer container = blobClient.GetContainerReference(container1);
CloudBlobDirectory dir = container.GetDirectoryReference(cameranaam);
CloudBlob cloudBlob = dir.GetBlobReference(cameranaam+".txt");
cloudBlob.UploadText(blobSAS.Uri.ToString());

And this is the timer of my other project who is loading the last image of the server:

blobClient = new CloudBlobClient(
    blobstoreurl, new StorageCredentialsSharedAccessSignature(signature));
container = blobClient.GetContainerReference(containerName);
CloudBlobDirectory dir = 
    container.GetDirectoryReference(comboBoxCameras.SelectedItem.ToString());
CloudBlob cloudBlob = dir.GetBlobReference(
    comboBoxCameras.SelectedItem.ToString().Replace(" ","") + ".txt");
pictureBoxLiveViewer.ImageLocation = cloudBlob.DownloadText() + signature;