C# downloading from Windows Azure Storage returns an empty file without any exceptions

Question

I'm trying to use Windows Azure Storage for my Windows Store App with Mobile Services to store images. I made uploading work by following this guide:

http://www.windowsazure.com/en-us/develop/mobile/tutorials/upload-images-to-storage-dotnet/

However, I couldn't find any material on downloading the files. I couldn't even find classes reference for windows store version! If someone could guide me to the documentation I would be grateful.

Anyway, I wrote the code but it doesn't seem work:

public static async System.Threading.Tasks.Task DownloadUserImage(SQLUser userData)
{
    var usersFolder = await GetUsersFolder();
    var imageUri = new Uri(userData.ImageUri);
    var accountName = "<SNIP>";
    var key = "<SNIP>";

    StorageCredentials cred = new StorageCredentials(accountName, key);
    CloudBlobContainer container = new CloudBlobContainer(new Uri(string.Format("https://{0}/{1}", imageUri.Host, userData.ContainerName)), cred);
    CloudBlockBlob blob = container.GetBlockBlobReference(userData.ResourceName);

    var imageFile = await usersFolder.CreateFileAsync(userData.Id.ToString() + ".jpg", CreationCollisionOption.ReplaceExisting);
    using (var fileStream = await imageFile.OpenAsync(FileAccessMode.ReadWrite))
    {
        try
        {
            await blob.DownloadToStreamAsync(fileStream);
        }
        catch (Exception e)
        {
            Tools.HandleLiveException(e);
        }
    }
}

This code results in empty file creation, but it doesn't throw any exceptions whatsoever. If I paste the value of imageUri to my browser, it starts downloading the file and completes the download successfully. However, my program does not, for some reason.

Any help, please?

Sunius Sunius · Accepted Answer · 2013-04-06T11:25:47

Apparently, I've been opening the stream in a wrong way. Here's a fix:

public static async System.Threading.Tasks.Task DownloadUserImage(SQLUser userData)
{
    var usersFolder = await GetUsersFolder();
    var imageUri = new Uri(userData.ImageUri);
    var accountName = "<SNIP>";
    var key = "<SNIP>";

    StorageCredentials cred = new StorageCredentials(accountName, key);
    CloudBlobClient client = new CloudBlobClient(new Uri(string.Format("https://{0}", imageUri.Host)), cred);
    CloudBlobContainer container = client.GetContainerReference(userData.ContainerName);
    var blob = await container.GetBlobReferenceFromServerAsync(userData.ResourceName);

    var imageFile = await usersFolder.CreateFileAsync(userData.Id.ToString() + ".jpg", CreationCollisionOption.ReplaceExisting);
    using (var fileStream = await imageFile.OpenStreamForWriteAsync())
    {
        try
        {
            await blob.DownloadToStreamAsync(fileStream.AsOutputStream());
        }
        catch (Exception e)
        {
            Tools.HandleLiveException(e);
        }
    }
}

It works perfectly now.

C# downloading from Windows Azure Storage returns an empty file without any exceptions

1 Answers