A VB.net Example showing how to create a time limited URL to access an Azure Blob

I needed to set up a quick download service for a file stored in Azure Blob Storage. As all examples for this were in C# I thought I’d post a VB.net example for anyone that needed it. The code is documented in the comments. The example also shows sending a HTML email with the URL embedded inside it.
Below is the MVC controller method which generates the URL and sends the email.

<HttpPost()>

Function RequestDownload(model As DownloadRequest) As ActionResult

    ' Get the storage account details from the configuration file.

    Dim storageAccount As CloudStorageAccount = CloudStorageAccount.Parse(ConfigurationManager.ConnectionStrings("BlobStorageConnectionString").ConnectionString)

    ' Create the container reference object

    Dim container As CloudBlobContainer = storageAccount.CreateCloudBlobClient().GetContainerReference("downloads")

    ' Create the blob reference object

    Dim blob = container.GetBlobReference(model.Filename)

    ' Calculate the time two minutes from now.

    Dim exTime As DateTime = DateTime.UtcNow + TimeSpan.FromMinutes(2)

    ' Now create a new shared access signature that expires two minutes

    ' from creation with Read only permissions.

    Dim sas = blob.GetSharedAccessSignature(New SharedAccessPolicy() With {

        .Permissions = SharedAccessPermissions.Read,

        .SharedAccessExpiryTime = exTime

    })

    ' Now create the URL

    Dim sasURL = blob.Uri.AbsoluteUri & sas

    ' Generate an email.

    ' Create the smtp object.

    Dim client As New SmtpClient("my.smtp.server")

    ' Now generate a new email message

    Dim message As New MailMessage

    message.From = New MailAddress("me@nobody.here.com")

    message.To.Add(New MailAddress(model.ToAddress))

    message.Subject = "Download link for " & model.Filename

    ' Make the html body of the email.

    message.IsBodyHtml = True

    Dim body = <Html>

                   <p>Click the below link to download <b><%= model.Filename %></b></p>

                   <p>This link will only be valid for two minutes from issue.</p>

                   <a href=<%= sasURL %>><%= sasURL %></a>

                   <p style="color: red;">Do not share this email link.</p>

                   <p>Regards</p>

                   <P>The Team</P>

               </Html>

    message.Body = body.ToString

    ' Now send.

    client.Send(message)

    Return RedirectToAction("Index")

End Function

Muhammad Rizwan

A VB.net Example showing how to create a time limited URL to access an Azure Blob