Azure Blob Storage - Using filestream/memorystream to display PDF

Question

I've set up an Azure Blob Storage to upload/download file.

ProcessAsync(Folderpath, rows.Item("FileName"), rows.Item("Extension")).GetAwaiter().GetResult()
System.IO.File.Move(Folderpath + "\" + rows.Item("FileName"), AchivePath + "\" + rows.Item("FileName"))
WriteToLog("Extracted File : " + rows.Item("FileName") + " ", "")
DownloadBlobSnapshot(rows.Item("FileName"), rows.Item("Extension")).GetAwaiter().GetResult()

Currently, I am able to store my file locally in my desktop. How do I save and display the file on .net MVC platform with Using and MemoryStream/FileStream?

Or alternatively, is there any better way in doing so?

Edit 1: (Based on Ivan's Answer)

Private Shared Async Function DownloadBlobSnapshot(FileName As String, Extension As String) As Task

Dim storageAccount As CloudStorageAccount
Dim storageConnectionString As String = ConfigurationManager.AppSettings("StorageConnectionString")
Dim accountName As String = myaccountname
Dim accountKey As String = myaccountkey
Dim cred = New StorageCredentials(accountName, accountKey)
Dim account = New CloudStorageAccount(cred, True)
Dim client = account.CreateCloudBlobClient()
Dim container = client.GetContainerReference(FileName.Replace(Extension, ""))
Dim listOfBlobs As IEnumerable = container.ListBlobs(Nothing, True, BlobListingDetails.Snapshots)

If CloudStorageAccount.TryParse(storageConnectionString, storageAccount) Then
   For Each item In listOfBlobs
       Dim blockBlob As CloudBlockBlob = container.GetBlockBlobReference((CType(item, CloudBlockBlob)).Name)
       blockBlob.DownloadToStream(Response.OutputStream)
   Next
       //ToDO
        End If
End Function

But I'd realised Response is not available in Shared Function.

Just want to clarify, you want to display the .pdf file in mvc page? and your .pdf file is stored locally or in the blob storage? — Ivan Glasenberg, Nov 23 '18 at 01:16
@IvanYang yes. I am storing it locally first then upload to blob storage. Afterwards I test it by downloading the same file and store it in different folder — PartTimeNerd, Nov 23 '18 at 01:23
I want to know that, if you wanna the .pdf file(stored in blob storage) to be displayed in a mvc page, right? — Ivan Glasenberg, Nov 23 '18 at 01:25
That should be easy if you use the method DownloadToStream, you can refer to my answer below. A minute later. — Ivan Glasenberg, Nov 23 '18 at 01:30

Ivan Glasenberg · Answer 1 · 2018-11-23T03:20:19.633

5

You can use DownloadToStream.

Sample code as below(asp.net mvc project):

        public ActionResult DownloadFile()
        {
            CloudStorageAccount storageAccount = new CloudStorageAccount(new StorageCredentials("your_account", "your_key"),true);
            CloudBlobClient client = storageAccount.CreateCloudBlobClient();
            CloudBlobContainer blobContainer = client.GetContainerReference("t11");
            CloudBlockBlob blob = blobContainer.GetBlockBlobReference("ss22.pdf");

            blob.DownloadToStream(Response.OutputStream);

            return new EmptyResult();
        }

Update 1: upload the screenshot of vb.net mvc project:

edited Nov 23 '18 at 03:20

answered Nov 23 '18 at 01:31

Ivan Glasenberg

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It's a vb.net project? I'm not familiar with it:( . But have you created an vb.net mvc project and write the code in xxxcontroller.vb? I create an vb.net mvc project, and the Response is ok there. Later, I will add the screenshot to my answer. – Ivan Glasenberg Nov 23 '18 at 03:17
Probably its due to my method declaration, seems like we can't use `Response` in a `shared` method – PartTimeNerd Nov 23 '18 at 03:48
Not sure because I'm not familiar with vb,if it's c#, I can do more investigation on it:) . – Ivan Glasenberg Nov 23 '18 at 04:02

PartTimeNerd · Accepted Answer · 2018-11-29T00:34:49.467

For those who've encountered the same issue as me.

Function DownloadBlobSnapshot(FileName As String, Extension As String) As ActionResult

    Dim storageAccount As CloudStorageAccount
    Dim storageConnectionString As String = ConfigurationManager.AppSettings("StorageConnectionString")
    Dim accountName As String = myaccountname
    Dim accountKey As String = myaccountkey
    Dim cred = New StorageCredentials(accountName, accountKey)
    Dim account = New CloudStorageAccount(cred, True)
    Dim client = account.CreateCloudBlobClient()
    Dim container = client.GetContainerReference("myfilename")
    Dim fileStream As New MemoryStream
    fileStream.Position = 0
    Dim listOfBlobs As IEnumerable = container.ListBlobs(Nothing, True, BlobListingDetails.Snapshots)

    Try
        If CloudStorageAccount.TryParse(storageConnectionString, storageAccount) Then
            For Each item In listOfBlobs
                Dim blockBlob As CloudBlockBlob = container.GetBlockBlobReference((CType(item, CloudBlockBlob)).Name)
                blockBlob.DownloadToStream(fileStream)
                Response.Clear()
                Response.ContentType = "application/force-download"
                Response.AddHeader("content-disposition", "inline; filename=name_you_file.pdf")
                Response.BinaryWrite(fileStream.ToArray)
                Response.End()

                Return New FileStreamResult(fileStream, "application/pdf")

            Next

        End If
    Catch ex As Exception

    End Try

End Function

Updated: 29/11/2018

Function DownloadBlobSnapshot(FilePath As String, LabCompany As String, FileName As String) As ActionResult

    Dim storageAccount As CloudStorageAccount
    Dim cloudBlobContainer As CloudBlobContainer = Nothing
    Dim sourceFile As String = Nothing
    Dim destinationFile As String = Nothing
    Dim storageConnectionString As String = (CASAuthentication.Decrypt(Configs.BlobConnectionString))
    Dim url As String = ""
    Dim sasToken As String = ""

    If CloudStorageAccount.TryParse(storageConnectionString, storageAccount) Then
        Try

            Dim cloudBlobClient As CloudBlobClient = storageAccount.CreateCloudBlobClient()

            cloudBlobContainer = cloudBlobClient.GetContainerReference(LabCompany.ToLower)
            If cloudBlobContainer.Exists() Then
                Dim cloudBlockBlob As CloudBlockBlob = cloudBlobContainer.GetBlockBlobReference((FileName))
                If cloudBlockBlob.Exists Then
                    url = cloudBlockBlob.Uri.AbsoluteUri()

                    Dim sharedPolicy As SharedAccessBlobPolicy = New SharedAccessBlobPolicy() With {
            .SharedAccessExpiryTime = DateTime.UtcNow.AddMinutes(Integer.Parse(ConfigurationManager.AppSettings("PDFTimeOut"))),
            .Permissions = SharedAccessBlobPermissions.Read Or SharedAccessBlobPermissions.Write
        }

                    sasToken = cloudBlockBlob.GetSharedAccessSignature(sharedPolicy)

                End If
            End If

                Return Json(New With {.success = True, .url = url + sasToken}, JsonRequestBehavior.AllowGet)

        Catch ex As Exception
            Return Json(New With {.success = False, .message = ex.ToString}, JsonRequestBehavior.AllowGet)
        Finally

        End Try

    Else
        Return Json(New With {.success = False, .message = "Failed to receive report data. Please try again later."}, JsonRequestBehavior.AllowGet)
    End If

End Function

Displaying using ajax

var tabledata =  {mydata: data}
    $.ajax({
        cache: false,
        type: "POST",
        url: "/Home/DownloadBlobSnapshot",
        contentType: "application/json; charset=utf-8",
        data: JSON.stringify(tabledata),
        success: function (result) {
            var e = result.url
            //e.substr(0, e.lastIndexOf("/"))
            e = "http://docs.google.com/viewer?url=" + encodeURIComponent(e) + "&embedded=true";
            popitup(e);
        },

        error: function () {

        }
    });

Azure Blob Storage - Using filestream/memorystream to display PDF

2 Answers2