reading content of blob from azure function

Question

I'm trying to read the content of a blob inside an azure function.

Here's the code:

Note: If I comment out the using block and return the blob i.e.

return new OkObjectResult(blob);

I get back the blob object.

However, if I use the using block, I get 500.

Any idea why I can't get the content?

string storageConnectionString = "myConnectionString";
CloudStorageAccount storageAccount;
CloudStorageAccount.TryParse(storageConnectionString, out storageAccount);
CloudBlobClient cloudBlobClient = storageAccount.CreateCloudBlobClient();
CloudBlobContainer container = cloudBlobClient.GetContainerReference("drawcontainer");


var blob = drawingsContainer.GetBlockBlobReference("notes.txt");

using (StreamReader reader = new StreamReader(blob.OpenRead()))
{
    content = reader.ReadToEnd();
}
return new OkObjectResult(content);

Anish K · Accepted Answer · 2019-08-02 19:54:55Z

1

HTTP 500 indicates that the code has error. The most probable reason for error is the variable 'content'. Define the variable 'content' outside the using block as the scope of the content variable defined inside it is limited to the block only. Declare it outside the using block, something like below:

    try
    {
        string content = string.Empty;
        using (StreamReader reader = new StreamReader(blob.OpenRead()))
        {
            content = reader.ReadToEnd();
        }
    }
    catch (Exception ex)
    {
        // Log exception to get the details.    
    }

Always make use of try catch to get more details about errors in the code.

answered Aug 2, 2019 at 19:54

Anish K

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4 Comments

Ace Over a year ago

Thanks for the answer. the variable content is not the issue (even though its declaration was missing). I placed try catch but didn't get a descriptive error

Ace Over a year ago

I placed some logs and I think the issue is the blob.OpenRead() - I think the OpenRead might not exists on the blob but I still didn't resolve the issue

Ace Over a year ago

The error that keep repeating is: error CS0103: The name 'CloudStorageAccount' does not exist in the current context

Anish K Over a year ago

@Avi Would you please provide the nuget package and the framework details? Also, please add/edit the complete code snippet.

Anish K · Accepted Answer · 2019-08-04 01:28:00Z

The OpenRead method didn't exist so I used the async one and it solved it.

I got to this solution after creating an azure function in VS and publishing it and it works.

Here's the code I used:

 public static class Function1
{
    [FunctionName("Function1")]
    public static async Task<ActionResult> Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)]HttpRequest req, TraceWriter log)
    {
        log.Info("C# HTTP trigger function processed a request.");
        string storageConnectionString = "DefaultEndpointsProtocol=https;AccountName=avitest19a1c;AccountKey=<AccessKey>";
        CloudStorageAccount storageAccount = null;
        CloudStorageAccount.TryParse(storageConnectionString, out storageAccount);
        CloudBlobClient cloudBlobClient = storageAccount.CreateCloudBlobClient();
        CloudBlobContainer drawingsContainer = cloudBlobClient.GetContainerReference("drawcontainer");

        var blob = drawingsContainer.GetBlockBlobReference("notes.txt");

        string content = string.Empty;
        **var contentStream = await blob.OpenReadAsync();**
        using (StreamReader reader = new StreamReader(contentStream))
        {
            content = reader.ReadToEnd();
        }

        return new OkObjectResult(content);

    }
}

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