Can I get a specific Block from an Azure Block Blob?

I want to get a specific block from an azure block blob with the blockId, is this even possible?
something like

var blockBlob = new BlockBlobClient(connectionString, containerName, blobName);
var blocklist = await GetBlobBlockList(blobName, cancellationToken);
var firstBlock = blocklist.First();
var memStream = new MemoryStream();
await blockBlob.DownloadStreamingAsync(memStream, firstBlock.Name);

> I want to get a specific block from an azure block blob with the
> blockId, is this even possible?

It should be possible to do so however it won't be as simple as you mentioned in your sample code.

Here's what you would need to do:

1. Fetch list of blocks. Each element in the list will have a block id and the size of the block.
2. Assuming you want to get data for block "n", what you will do is iterate over the list from 0 to n - 1 block and add the size of each block.
3. Next you would need to call DownloadRangeToStreamAsync(Stream, Nullable<Int64>, Nullable<Int64>), where your offset value will be the sum of the size of each block calculated in step 2 and length value will be the size of the block you wish to download.

You need to create a block blob below you can find the procedure:

you need to create a container under storage account as follows:

inside the container you can find the block blob under properties as shown below

To Get the block Id you can follow the code below:

code:

using System;  
using System.Threading.Tasks;  
using Azure.Storage.Blobs;  
using Azure.Storage.Blobs.Models;

class Program  
{  
static async Task Main(string[] args)  
{  
string connectionString = "DefaultEndpointsProtocol=https;AccountName=<account-name>;AccountKey=<account-key>;EndpointSuffix=core.windows.net";  
string containerName = "***";  
string blobName = "***.txt";  
BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);  
BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(containerName);  
BlobClient blobClient = containerClient.GetBlobClient(blobName);

  
BlockList blockList = await blobClient.GetBlockListAsync(BlockListType.All)  
string firstBlockId = blockList.Value.First().Name;  
Console.WriteLine("First block ID: " + firstBlockId);  
}  
}

After getting the Block Id now you can get the certain block using the code below:

code:

using System;  
using System.IO;  
using System.Threading;  
using System.Threading.Tasks;  
using Azure.Storage.Blobs;  
using Azure.Storage.Blobs.Models;

class Program  
{  
static async Task Main(string[] args)  
{  
string connectionString = "DefaultEndpointsProtocol=https;AccountName=<account-name>;AccountKey=<account-key>;EndpointSuffix=core.windows.net";  
string containerName = "mycontainer---";  
string blobName = "myblob**";  
string blockId = "1234567**";  
BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);  
BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(containerName);  
BlobClient blobClient = containerClient.GetBlobClient(blobName);  
MemoryStream blockData = new MemoryStream();  
await blobClient.DownloadStreamingAsync(blockId, blockData, cancellationToken: CancellationToken.None);  
Console.WriteLine("Block data:");  
Console.WriteLine(Convert.ToBase64String(blockData.ToArray()));  
}  
}

In the above code you need to replace connection string, container name, block Id, blob name as below:

By following the above procedure, I got successfully.