CODEWITHSUNDEEP
c#jsonazureazure-blob-storage
Michael Sabin
Michael Sabin

Reputation: 1759

CloudBlockBlob.DownloadTextAsync returns invalid text

I am using azure blob storage to store a JSON file and in my code I download it using the C# APIs.

When I download the contents of the text file and attempt to Deserialize it using JsonConvert, I get an error (the Visual Studio JSON visualizer also shows an error for the text). However, if I copy the text and paste into JSONLint.com it appears fine. Also, If I manually download the file from Azure Storage and read the file in code, it deserializes just fine. Any ideas why I am getting invalid data when I download using the C# APIs?

var storageAccount = CloudStorageAccount.Parse(connectionString);
var blobClient = storageAccount.CreateCloudBlobClient();
var container = blobClient.GetContainerReference(containerName);
var blob = container.GetBlockBlobReference(folderAndFileName);
var text =  await blob.DownloadTextAsync();
var obj = JsonConvert.DeserializeObject(text);
// Exception: "Unexpected character encountered while parsing value: . Path '', line 0, position 0."

Note: I am uploading the file via Powershell:

$blobProperties = @{"ContentType" = "application/json"};
Set-AzureStorageBlobContent -Container $containerName -File  $LocalFilePath -Blob $RemoteBlobName -BlobType "Block" -Properties $blobProperties

Upvotes: 6

Views: 1572

Answers (2)

Michael Sabin
Michael Sabin

Reputation: 1759

After further investigation, I found that the downloaded file has an extra Unicode formatting character at the start. I added the following code to just check for special characters at the beginning and remove them...

var startIndex = 0;
while (char.GetUnicodeCategory(text, startIndex) == UnicodeCategory.Format)
{
     startIndex++;
}
text = text.Substring(startIndex, text.Length - startIndex);

Upvotes: 3

Jambor - MSFT
Jambor - MSFT

Reputation: 3293

I have tested your code. It seems that this issue is not about your code. The following is my tested result with your code:

enter image description here

Entity:

    public class People
    {
        [JsonProperty(PropertyName ="name")]
        public string Name { get; set; }
        [JsonProperty(PropertyName = "address")]
        public string  Address { get; set; }
    }

Json File:

{
  "name": "jambor",
  "address": "us"
}

As Gaurav Mantri said, I would suggest you check your storage library. The version of my Azure storage library is 7.2.1. Please also set breakpoint at the code var obj = JsonConvert.DeserializeObject(text);. Then check the value of text. It may help you to find out the issue.

Upvotes: 1

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