Is it possible to download a specific block from an Azure Block Blob if you know the Block Id?
Yes, you absolutely can, here's an example of how to download the first block:
var storageAccount = CloudStorageAccount.Parse("DefaultEndpointsProtocol=https;AccountName=...;AccountKey=...;EndpointSuffix=core.windows.net");
CloudBlobClient serviceClient = storageAccount.CreateCloudBlobClient();
var container = serviceClient.GetContainerReference("containerName");
var blockBlob = container.GetBlockBlobReference("blobName");
var blocklist = await blockBlob.DownloadBlockListAsync();
var firstBlock = blocklist.First();
var memStream = new MemoryStream();
await blockBlob.DownloadRangeToStreamAsync(memStream, 0, firstBlock.Length);
string contents;
using (var streamReader = new StreamReader(memStream))
{
contents = await streamReader.ReadToEndAsync();
}
You will need a couple of packages from nuget:
Microsoft.WindowsAzure.Storage
Microsoft.WindowsAzure.Storage.Blob
You could leverage Microsoft Azure Storage SDK for getting started with Azure Blob Storage quickly. And the Azure Storage SDK is a wrapper of Blob Service REST API. From the official tutorial about Blob Service REST API, we couldn't find anything about downloading the specific block via the Block Id. In addition, you could use Get Blob to download the bytes of your blob in the specified range by specifying the offset and the length of data to download from your blob.
Related
I have prepared some C# code to create a container in the Azure Storage and then I am uploading a file into that azure container. The code is below:
var connectionString = _settings.appConfig.StorageConnectionString;
BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);
BlobContainerClient blobContainer = blobServiceClient.GetBlobContainerClient("nasir-container");
await blobContainer.CreateIfNotExistsAsync(); // Create the container.
BlobClient blobClient = blobContainer.GetBlobClient(fileName); // Creating the blob
string fileName = "D:/Workspace/Adappt/MyWordFile.docx";
FileStream uploadFileStream = System.IO.File.OpenRead(fileName);
blobClient.Upload(uploadFileStream);
uploadFileStream.Close();
Now I have updated my MyWordFile.docx with more content. Now I would like to upload this updated file to the same blob storage. How can I do this? I also want to create versioning too so that I can get the file content based on the version.
Now I have updated my MyWordFile.docx with more content. Now I would
like to upload this updated file to the same blob storage. How can I
do this?
To update a blob, you simply upload the same file (basically use the same code you wrote to upload the file in the first place). Upload operation will overwrite an existing blob.
I also want to create versioning too so that I can get the file
content based on the version.
There are two ways you can implement versioning for blobs:
Automatic versioning: If you want Azure Blob Storage service to maintain versions of your blobs, all you need to do is enable versioning on the storage account. Once you enable that, anytime a blob is modified a new version of the blob will be created automatically for you by service. Please see this link to learn more about blob versioning: https://learn.microsoft.com/en-us/azure/storage/blobs/versioning-overview.
Manual versioning: While automatic versioning is great but there could be many reasons why you would want to opt for manual versioning (e.g. you only want to version a few blobs and not all blobs, you are not using V2 Storage account etc.). If that's the case, then you can create a version of the blob by taking a snapshot of the blob before you update the blob. Snapshot creates a read-only copy of the blob at the point of time snapshot was taken. Please see this link to learn more about blob snapshot: https://learn.microsoft.com/en-us/azure/storage/blobs/snapshots-overview.
First you need to enable versioning in the blob storage through the portal in the storage account.
Just click on Disable it will take you to a different page and select enable version and click save
Here after uploading the blob when you update the blob it will automatically trigger the creating of versions.
public static async Task UpdateVersionedBlobMetadata(BlobContainerClient blobContainerClient,
string blobName)
{
try
{
// Create the container.
await blobContainerClient.CreateIfNotExistsAsync();
// Upload a block blob.
BlockBlobClient blockBlobClient = blobContainerClient.GetBlockBlobClient(blobName);
string blobContents = string.Format("Block blob created at {0}.", DateTime.Now);
byte[] byteArray = Encoding.ASCII.GetBytes(blobContents);
string initalVersionId;
using (MemoryStream stream = new MemoryStream(byteArray))
{
Response<BlobContentInfo> uploadResponse =
await blockBlobClient.UploadAsync(stream, null, default);
// Get the version ID for the current version.
initalVersionId = uploadResponse.Value.VersionId;
}
// Update the blob's metadata to trigger the creation of a new version.
Dictionary<string, string> metadata = new Dictionary<string, string>
{
{ "key", "value" },
{ "key1", "value1" }
};
Response<BlobInfo> metadataResponse =
await blockBlobClient.SetMetadataAsync(metadata);
// Get the version ID for the new current version.
string newVersionId = metadataResponse.Value.VersionId;
// Request metadata on the previous version.
BlockBlobClient initalVersionBlob = blockBlobClient.WithVersion(initalVersionId);
Response<BlobProperties> propertiesResponse = await initalVersionBlob.GetPropertiesAsync();
PrintMetadata(propertiesResponse);
// Request metadata on the current version.
BlockBlobClient newVersionBlob = blockBlobClient.WithVersion(newVersionId);
Response<BlobProperties> newPropertiesResponse = await newVersionBlob.GetPropertiesAsync();
PrintMetadata(newPropertiesResponse);
}
catch (RequestFailedException e)
{
Console.WriteLine(e.Message);
Console.ReadLine();
throw;
}
}
static void PrintMetadata(Response<BlobProperties> propertiesResponse)
{
if (propertiesResponse.Value.Metadata.Count > 0)
{
Console.WriteLine("Metadata values for version {0}:", propertiesResponse.Value.VersionId);
foreach (var item in propertiesResponse.Value.Metadata)
{
Console.WriteLine("Key:{0} Value:{1}", item.Key, item.Value);
}
}
else
{
Console.WriteLine("Version {0} has no metadata.", propertiesResponse.Value.VersionId);
}
}
The above code is from the following documentation.
I am trying to get a file from Azure container. I need to read its content.
The file has been uploaded to umbraco media, media are stored in our Azure container.
Its normal (umbraco) url would be like:
~/media/10890/filename.xls
I am trying to retrieve it like this:
var storageAccount = CloudStorageAccount.Parse(ConfigurationManager.AppSettings["strorageconnstring"]);
var blobClient = storageAccount.CreateCloudBlobClient();
var container = blobClient.GetContainerReference("storagemedia");
The thing is - I am not sure how I am supposed to retrieve a particular file? I tried:
1.
CloudBlobDirectory dira = container.GetDirectoryReference("10890"); // file folder within media
var list = dira2.ListBlobs(useFlatBlobListing: true).ToList(); // Returns error saying "The requested URI does not represent any resource on the server."
However the 10890 folder within media storage exists and I can browse it with storage browser.
2.
CloudBlockBlob blobFile = container.GetBlockBlobReference("10890/filename.xls");
string text;
using (var memoryStream = new MemoryStream())
{
blobFile.DownloadToStream(memoryStream); // Throws "The specifed resource name contains invalid characters." error
var length = memoryStream.Length;
text = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray());
}
Any idea how to read the file? And what am I doing wrong?
Thank You Gaurav for providing your suggestion in comment section.
Thank You nicornotto for confirming that your issue got resolved by changing the container name reference in the below statement.
var container = blobClient.GetContainerReference("storagemedia");
This question already has answers here:
How upload blob in Azure Blob Storage with specified ContentType with .NET v12 SDK?
(2 answers)
Closed 2 years ago.
I'm using the asp.net-core webapi to upload images to azure storage.
I was able to successfully upload a image blob to azure storage (using the quickstart). However, the content-type property (with azure) is set to application/octet-stream. The problem with this is the public url will not load in a browser due to this content type. I plan to eventually consume this url/image in my website so I'm thinking this might work. Is there any way to specify the CONTENT-TYPE to image/jpeg? I've also tried the following code but received error message: 404 (The specified blob does not exist.) during the SetHttpHeaders call (the UploadBlob method call that is currently commented out does work, but has the octet-stream content type).
BlobClient blobClient = containerClient.GetBlobClient(guids[index]);
using (var content = file.OpenReadStream())
{
blobClient.Upload(content);
blobClient.SetHttpHeaders(new BlobHttpHeaders() { ContentType = "image/jpeg" });
//containerClient.UploadBlob(guids[index], content);
}
Not specific contentType, with the filename.[ext] download ok. When create the reference to blobclient set the extension. Example download:
var fileName = $"{guids[index]}.jpg";
var pathStorage = Path.Combine(path, fileName);
BlobClient blobClient = containerClient.GetBlobClient(pathStorage);
BlobDownloadInfo download = await blobClient.DownloadAsync();
byte[] bytesContent;
using (var ms = new MemoryStream())
{
await download.Content.CopyToAsync(ms);
bytesContent = ms.ToArray();
}
return bytesContent;
Example upload:
var fileName = $"{guids[index]}.jpg";
var pathStorage = Path.Combine(path, fileName);
BlobClient blobClient = containerClient.GetBlobClient(pathStorage);
var stream = new MemoryStream(bytesContent);
var uploadInfo = await blobClient.UploadAsync(stream);
I'm trying to use nuget Microsoft.Azure.CognitiveServices.Knowledge.QnAMaker to use QnAMakerClient and Knowledgebase.DownloadWithHttpMessagesAsync, but when I try to instantiate Microsoft.Azure.CognitiveServices.Knowledge.QnAMaker() the parameters are the abstract classes, so I don't know how I can use QnAMakerClient to download the contents of Body.QnaDocuments.
Microsoft.Azure.CognitiveServices.Knowledge.QnAMaker.QnAMakerClient z = new Microsoft.Azure.CognitiveServices.Knowledge.QnAMaker.QnAMakerClient(new ServiceClientCredentials(),HttpClient httpClient, bool disposeHttpClient);
var kb = z.Knowledgebase.DownloadWithHttpMessagesAsync("key", "test").Result;
Thanks for your help.
#elise You can find one example on how to download the knowledgebase here.
Essentially:
var client = new QnAMakerClient(new ApiKeyServiceClientCredentials(key)) { Endpoint = endpoint };
// Download the KB
Console.Write("Downloading KB...");
var kbData = await client.Knowledgebase.DownloadAsync(kbId, EnvironmentType.Prod);
Console.WriteLine("KB Downloaded. It has {0} QnAs.", kbData.QnaDocuments.Count);
I got an assignment to see if I can make power app that will generate some PDF file for end user to see.
After through research on this topic I found out that this is not an easy to achieve :)
In order to make power app generate and download/show generated pdf I made these steps:
Created power app with just one button :) to call Azure function from step 2
Created Azure function that will generate and return pdf as StreamContent
Due to power app limitations (or I just could not find the way) there was no way for me to get pdf from response inside power app.
After this, I changed my Azure function to create new blob entry but know I have problem to get URL for that new entry inside Azure function in order to return this to power app and then use inside power app Download function
My Azure function code is below
using System;
using System.Net;
using System.Net.Http.Headers;
using System.Runtime.InteropServices;
using Aspose.Words;
public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log, Stream outputBlob)
{
log.Info($"C# HTTP trigger function processed a request. RequestUri={req.RequestUri}");
var dataDir = #"D:/home";
var docFile = $"{dataDir}/word-templates/WordAutomationTest.docx";
var uid = Guid.NewGuid().ToString().Replace("-", "");
var pdfFile = $"{dataDir}/pdf-export/WordAutomationTest_{uid}.pdf";
var doc = new Document(docFile);
doc.Save(pdfFile);
var result = new HttpResponseMessage(HttpStatusCode.OK);
var stream = new FileStream(pdfFile, FileMode.Open);
stream.CopyTo(outputBlob);
// result.Content = new StreamContent(stream);
// result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
// result.Content.Headers.ContentDisposition.FileName = Path.GetFileName(pdfFile);
// result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
// result.Content.Headers.ContentLength = stream.Length;
return result;
}
I left old code (the one that streams pdf back under comments just as reference of what I tried)
Is there any way to get download URL for newly generated blob entry inside Azure function?
Is there any better way to make power app generate and download/show generated PDF?
P.S. I tried to use PDFViewer control inside power app, but this control is completely useless cause U can not set Document value via function
EDIT: Response from #mathewc helped me a lot to finally wrap this up. All details are below.
New Azure function that works as expected
#r "Microsoft.WindowsAzure.Storage"
using System;
using System.Net;
using System.Net.Http.Headers;
using System.Runtime.InteropServices;
using Aspose.Words;
using Microsoft.WindowsAzure.Storage.Blob;
public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log, CloudBlockBlob outputBlob)
{
log.Info($"C# HTTP trigger function processed a request. RequestUri={req.RequestUri}");
var dataDir = #"D:/home";
var docFile = $"{dataDir}/word-templates/WordAutomationTest.docx";
var uid = Guid.NewGuid().ToString().Replace("-", "");
var pdfFile = $"{dataDir}/pdf-export/WordAutomationTest_{uid}.pdf";
var doc = new Document(docFile);
doc.Save(pdfFile);
var result = new HttpResponseMessage(HttpStatusCode.OK);
var stream = new FileStream(pdfFile, FileMode.Open);
outputBlob.UploadFromStream(stream);
return req.CreateResponse(HttpStatusCode.OK, outputBlob.Uri);
}
REMARKS:
Wee need to add "WindowsAzure.Storage" : "7.2.1" inside project.json. This package MUST be the same version as one with same name that is in %USERPROFILE%\AppData\Local\Azure.Functions.Cli
If you change your blob output binding type from Stream to CloudBlockBlob you will have access to CloudBlockBlob.Uri which is the blob path you require (documentation here). You can then return that Uri back to your Power App. You can use CloudBlockBlob.UploadFromStreamAsync to upload your PDF Stream to the blob.