Open a pdf file(using bytes) stored in Azu

问题:

I am trying to tweak the old logic to support files from blob, Can anyone guide me how to open a pdf file which is stored in azure blob storage.

I tried to search and found the answer How to download a file to browser from Azure Blob Storage which is using SAS configuration to do that (if i am not wrong).

Is there any way to do by converting to bytes?

Earlier logic to open a pdf file from windows location

Response.Buffer = true;
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.ContentType = "application/pdf";
Response.AppendHeader("content-disposition", "inline; filename=" + mapid + ".pdf");

FileStream fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
BinaryReader br = new BinaryReader(fs);
Byte[] dataBytes = br.ReadBytes((int)(fs.Length - 1));
Response.BinaryWrite(dataBytes);
br.Close();
fs.Close();

I am rewritting the logic to read the file from blob, below code is what i have tried so far,

Byte[] dataBytes1;
CloudBlockBlob blobfile = GetStorageAccount(true).GetBlockBlobReference(filename);
blobfile.FetchAttributes();

using (StreamReader blobfilestream = new StreamReader(blobfile.OpenRead()))
{
    dataBytes1 = blobfilestream.CurrentEncoding.GetBytes(blobfilestream.ReadToEnd());
}
Byte[] value = BitConverter.GetBytes(dataBytes1.Length - 1);
Response.BinaryWrite(value);

But the file is not opening with error "Failed to Load". Can anyone guide me if this is good approach to do it?

回答1:

You could use DownloadToStreamAsync and use the Response.OutputStream as the destination stream.

await blob.DownloadToStreamAsync(Response.OutputStream);

回答2:

You can use DownloadToByteArray, sample code(in asp.net mvc project) as below, and works fine at my side:

        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.FetchAttributes();

            long fileByteLength = blob.Properties.Length;
            byte[] fileContent = new byte[fileByteLength];
            for (int i=0;i<fileByteLength;i++)
            {
                fileContent[i] = 0x20;
            }

            blob.DownloadToByteArray(fileContent,0);

            Response.BinaryWrite(fileContent);

            return new EmptyResult();
        }

Or as per @hardkoded mentioned, you can either use DownloadToStreamAsync or DownloadToStream per your need.

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();
        }

The test result as below:

回答3:

As hardkoded mentioned above, you need to use DownloadToStreamAsync. Below is my code.

        blobfile.FetchAttributes();

        using (StreamReader blobfilestream = new StreamReader(blobfile.OpenRead()))
        {
            dataBytes1 = blobfilestream.CurrentEncoding.GetBytes(blobfilestream.ReadToEnd());
            await blobfile.DownloadToStreamAsync(Response.OutputStream);
        }

        Byte[] value = BitConverter.GetBytes(dataBytes1.Length - 1);
        string mimeType = "application/pdf";
        Response.AppendHeader("Content-Disposition", "inline; filename="+ filename);

        return File(value, mimeType);

回答4:

     public async System.Threading.Tasks.Task<ActionResult> DownloadFile()
    {
        CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
        ConfigurationManager.ConnectionStrings["azureconnectionstring"].ConnectionString);
        CloudBlobClient client = storageAccount.CreateCloudBlobClient();
        CloudBlobContainer blobContainer = client.GetContainerReference("my-blob-storage");
    CloudBlockBlob blob = blobContainer.GetBlockBlobReference("filename.pdf");
        var exists = blob.Exists(); // to verify if file exist
        blob.FetchAttributes();
        byte[] dataBytes1;
        using (StreamReader blobfilestream = new StreamReader(blob.OpenRead()))
        {
            dataBytes1 = blobfilestream.CurrentEncoding.GetBytes(blobfilestream.ReadToEnd());
            await blob.DownloadToStreamAsync(Response.OutputStream);
        }

        Byte[] value = BitConverter.GetBytes(dataBytes1.Length - 1);
        string mimeType = "application/pdf";
        Response.AppendHeader("Content-Disposition", "inline; filename=" + "filename.pdf");

        return File(value, mimeType);

}