How to Unzip Azure Blobs programmatically using Memory Streams in Azure WebJOBs | José Quinto

Introduction

Recently I had to extract files from a .zip file stored on Azure Blob Storage in Azure WebJob process.

The approach

This is what I did from scratch:

1. Create WebJob project

2. Create Non-continuous Azure WebJob

   static void Main()
   {
     var host = new JobHost();
     host.Call(typeof(Functions).GetMethod(“MyMethod”));
   }
   
   public class Functions
   {
     [NoAutomaticTrigger]
     public static void MyMethod()
     {
       // code
     }
   }

3. Install WindowsAzure.ConfigurationManager and WindowsAzure.Storage nuget packages.

   Install-Package Microsoft.WindowsAzure.ConfigurationManager
   Install-Package WindowsAzure.Storage

4. Add System.IO.Compression.dll from system dlls.

5. Add this code:

   	using System;
   	using System.Collections.Generic;
   	using System.IO;
   	using System.Linq;
   	using Microsoft.Azure.WebJobs;
   	using Microsoft.WindowsAzure;
   	using Microsoft.WindowsAzure.Storage.Blob;
   	using System.IO.Compression;
   	namespace MyWebJobNamespace
   	{
   	// Functions.cs file
   	public class Functions
   	{
   	[NoAutomaticTrigger]
   	public static void MyMethod()
   	{
   	// Retrieve storage account from connection string.
   	CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"));
   	// Stored on App.config or Azure WebApp UI Settings. CloudConfigurationManager is able to retrieve from these two places)
   	//<appSettings>
   	// <add key="StorageConnectionString" value="DefaultEndpointsProtocol=https;AccountName=storageAccountName;AccountKey=storageAccountKey" />
   	//</appSettings>
   	// Create the blob client.
   	CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
   	// Retrieve reference to a previously created container.
   	CloudBlobContainer container = blobClient.GetContainerReference("containerName");
   	// Retrieve reference to a blob name
   	CloudBlockBlob blockBlob = container.GetBlockBlobReference("MyFile.zip");
   	// Save blob contents to a Memory Stream.
   	using (var msZippedBlob = new MemoryStream())
   	{
   	blockBlob.DownloadToStream(msZippedBlob);
   	using (ZipArchive zip = new ZipArchive(msZippedBlob))
   	{
   	var entry = zip.Entries.First();
   	using (StreamReader sr = new StreamReader(entry.Open()))
   	{
   	string result = sr.ReadToEnd();
   	System.Console.WriteLine("# Characters: " + result.Length);
   	}
   	}
   	}
   	}
   	}
   	}

   view raw JQ.Azure.WebJob.UnzipBlob.cs hosted with ❤ by GitHub

Important notes

• Previously we need to create Azure Storage Account and get the storageAccountName and storageAccountKey.
• CloudConfigurationManager is able to retrieve settings firdt from Azure WebApp Settings UI and secondly from App.config file.
• We must create a new Blob Container and change in the code (or add a new app setting).
• ZipArchive is the system native approach to unzip files.
• Isn’t needed store temporary files to unzip and I have tested files until 150 MB (10MB compressed) on WebJobs working fine.