Download a Blob in JavaScript

Question

I have created an Azure Cloud Service with a WCF REST service. I am working on the local storage development with blobs. At this time, I've been able to upload files from my computer in containers and list them as well in a Listbox1. Now, i need to select an item(blob) from my Listbox1 and download the selected item. Here's my code:

public void DownloadBlob(AzureDataContract download) { // Connect to the storage account's blob endpoint CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("AzureStorageConnectionString")); CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient(); // Create the blob storage container CloudBlobContainer container = blobClient.GetContainerReference(download.ContainerName); container.CreateIfNotExists(); // Create the blob in the container CloudBlockBlob blob = container.GetBlockBlobReference("test"); using (var fileStream = System.IO.File.OpenWrite(download.FilePath)) { blob.DownloadToStream(fileStream); } }

Then i am trying to call my method using JQuery and Ajax as follow:

$('#btnDownload').click(function() { var download = { "ContainerName": $("#listContainer").val(), "FilePath": $("#listBlob option:selected").val() }; $.ajax({ type: "POST", url: "http://localhost:49416/AzureService.svc/DownloadBlob", data: JSON.stringify(download), contentType: "application/json; charset=utf-8", dataType: "json", processData: true, success: function(data) { alert("downloading"); }, error: function(data) { alert("error"); } }); });

Yes, i have this problem: An exception of type 'System.UnauthorizedAccessException' occurred in mscorlib.dll but was not handled in user code Additional information: Access to the path 'C:\' is denied. I have create an input where i set my path — Huby03
– Huby03, Commented Feb 27, 2016 at 19:48

Peter · Accepted Answer · 2016-02-27 16:31:52Z

At this moment your DownloadBlob function is not returning anything. It is a void function. So your client will never receive the blob. What it is doing at the moment is writing the blob to a file on the server disk (download.FilePath). If you want to download anything in your rest call, you should return the file to the client.

Alex Chen-WX · Accepted Answer · 2016-02-29 07:05:28Z

Your code looks fine. After running, the blob file should have been downloaded to your 'FilePath' location. 'System.UnauthorizedAccessException' normally happened when you have no right to delete/create a file under a folder. I think you can check if you have write access to "FilePath' position.

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