Azure Iterate through Blobs in a container

Question

I'm trying through iterate through blobs from a container, but I'm getting errors. I'm using the following code from Microsoft Docs: One of the main errors I'm getting is when calling the ToListAsync() method

// Iterate through the blobs in a container
List<BlobItem> segment = await blobContainer.GetBlobsAsync(prefix: "").ToListAsync();
foreach (BlobItem blobItem in segment)
{
    BlobClient blob = blobContainer.GetBlobClient(blobItem.Name);
    // Check the source file's metadata
    Response<BlobProperties> propertiesResponse = await blob.GetPropertiesAsync();
    BlobProperties properties = propertiesResponse.Value;
    
    // Check the last modified date and time
    // Add the blob to the list if has been modified since the specified date and time
    if (DateTimeOffset.Compare(properties.LastModified.ToUniversalTime(), transferBlobsModifiedSince.ToUniversalTime()) > 0)
    {
        blobList.Add(blob);
    }
}

These are the errors: enter image description here

enter image description here

What is the error? Please provide the exact text of the error message and indicate what line it came from. — Daniel Mann
– Daniel Mann, Commented Jun 22, 2022 at 21:17

StriplingWarrior · Accepted Answer · 2022-06-22 23:26:43Z

1

From https://learn.microsoft.com/en-us/dotnet/azure/sdk/pagination#use-systemlinqasync-with-asyncpageable

The System.Linq.Async package provides a set of LINQ methods that operate on IAsyncEnumerable<T> type. Because AsyncPageable<T> implements IAsyncEnumerable<T>, you can use System.Linq.Async to query and transform the data.

So make sure you have the System.Linq.Async package included in your project, along with a using System.Linq.Async; directive in your C# file.

Just be aware that there's a reason this is using an IAsyncEnumerable<>: if you have a lot of blobs it might be better to stream your way through the collection rather than loading all the values into an in-memory list.

IAsyncEnumerable<BlobItem> segment = blobContainer.GetBlobsAsync(prefix: "");
await foreach (BlobItem blobItem in segment)
{
    ...
}

answered Jun 22, 2022 at 23:26

StriplingWarrior

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