Azure download blob to users computer - asp.net-mvc

Question

I was working on my download blob function when I ran into some problems..
I want the user to be able to download a blob and I want a specific filename on that item when its downloaded to the users computer. I also want the user to decide which folder the item should be saved to.
This is my not so good looking code so far:
var fileName = "tid.txt9c6b412a-270a-4f67-8e65-7ce2bf87503d";
var containerName = "uploads";
CloudStorageAccount account = CloudStorageAccount.DevelopmentStorageAccount;
var blobClient = account.CreateCloudBlobClient();
var container = blobClient.GetContainerReference(containerName);
var blob = container.GetBlockBlobReference(fileName);
using (var filestream = System.IO.File.OpenWrite(#"C:\Info\tid.txt9c6b412a-270a-4f67-8e65-7ce2bf87503d"))
{
blob.DownloadToStream(filestream);
}
fileName = the blob name
Is it possible to change the name? The file ending gets all messed up with my guid.
At the moment the download to folder is C:\Info.. How would this work when the website is published? How can I let the user decide which folder the item should be saved to? Am i doing this right?
thank you in advance
/Filip

Answer 1

How would this work when the website is published?
Slow for the user and expensive for you. You are streaming the BLOB through your app, so you'll bottleneck. Use Shared Access Signatures and download the blob directly from the browser. Use Content-Disposition as part of the URL to have the browser prompt the user with a Save As dialog. See Javascript download a URL - Azure Blob Storage.

Answer 2

Your question: Is it possible to change the name?
The name of the blob and the name on the user's disk are your/his choice. There is no need for them to match, except perhaps to avoid confusion. On the off chance that your user will upload it again (with changes, perhaps?) save some metadata so the original file and the updated file can be related in blob storage.
Once you execute the line:
var blob = container.GetBlockBlobReference(fileName);
... you have told Azure all it needs to know to locate the blob.
In the line:
using (var filestream = System.IO.File.OpenWrite...
... you tell your code where to put the file on the disk. You say it's a website, so this statement will put the file onto the web server's disk, not your user's. To get the file onto the user's disk, you need one more step - download the file from the web server (web role instance) to your user's computer. You can give him control of the folder and file name. Here is the relevant section in MSDN:
Downloading and Uploading Files

Answer 3

Is this download function acceptable? Slow/expensive or is it as good as it gets?
public void DownloadFile(string blobName)
{
CloudBlobContainer blobContainer = CloudStorageServices.GetCloudBlobsContainer();
CloudBlockBlob blob = blobContainer.GetBlockBlobReference(blobName);
MemoryStream memStream = new MemoryStream();
blob.DownloadToStream(memStream);
Response.ContentType = blob.Properties.ContentType;
Response.AddHeader("Content-Disposition", "Attachment; filename=" + blobName.ToString());
Response.AddHeader("Content-Length", (blob.Properties.Length - 1).ToString());
Response.BinaryWrite(memStream.ToArray());
Response.End();
}