Writing to Azure Block Blobs

Question

I am using PutBlock and PutBlockList to upload data to a block blob, the code i am using for this is below:-

CloudBlobContainer container = blobStorage.GetContainerReference("devicebackups");
var permissions = container.GetPermissions();
permissions.PublicAccess = BlobContainerPublicAccessType.Container;
container.SetPermissions(permissions);
CloudBlockBlob blob = container.GetBlockBlobReference(serialNo.ToLower() + " " + dicMonths[DateTime.Now.Month]);
try
{
    var serializer = new XmlSerializer(typeof(List<EnergyData>));
    var stringBuilder = new StringBuilder();
    using (XmlWriter writer = XmlWriter.Create(stringBuilder))
    {
        try
        {
            serializer.Serialize(writer, deviceData);
            byte[] byteArray = Encoding.UTF8.GetBytes(stringBuilder.ToString());

            List<string> blockIds = new List<string>();
            try 
            { 
                blockIds.AddRange(blob.DownloadBlockList(BlockListingFilter.Committed).Select(b => b.Name)); 
            }
            catch (StorageClientException e)
            {
                if (e.ErrorCode != StorageErrorCode.BlobNotFound)
                {
                    throw;
                }
                blob.Container.CreateIfNotExist();
            }
            var newId = Convert.ToBase64String(Encoding.UTF8.GetBytes(blockIds.Count().ToString()));
            blob.PutBlock(newId, new MemoryStream(byteArray), null);
            blockIds.Add(newId);
            blob.PutBlockList(blockIds);
        }
        catch (Exception ex) 
        { 
            UT.ExceptionReporting(ex, "Error in Updating Backup Blob - writing byte array to blob"); 
        }
    }
}
catch (Exception ex) 
{ 
    UT.ExceptionReporting(ex, "Error in Updating Backup Blob - creating XmlWriter"); 
}
}
catch (Exception ex) 
{ 
    UT.ExceptionReporting(ex, "Error in Updating Backup Blob - getting container and blob references, serial no -" + serialNo); 
}

This works for 10 blocks, then on the 11th block it crashes with the following error:-

StorageClientException - The specified block list is invalid.

InnerException = {"The remote server returned an error: (400) Bad Request."}

I have searched the internet for reports of the same error, but had no luck.

Any help would be much appreciated.

Answer 1

For a given blob, the length of the value specified for the blockid parameter must be the same size for each block.

http://msdn.microsoft.com/en-us/library/windowsazure/dd135726.aspx

The first 10 blocks are numbered 0 through 9. The 11th block is number 10, which is longer by one character. So you should change your numbering scheme to always use the same length. One solution would be to convert the count to a zero-padded string that's long enough to hold the number of blocks you expect to have.

But if you don't need the benefits of using blocks, you're probably better off just writing the whole blob in one go instead of using blocks.

Answer 2

Set your BlockID has below code

var blockIdBase64 = Convert.ToBase64String(Encoding.UTF8.GetBytes(blockId.ToString(CultureInfo.InvariantCulture).PadLeft(32, '0')));