Upload and Retrieve File from Azure Blob Storage in C# & VB for .NET Framework

Azure Blob Storage is one of the Microsoft Azure Resource to store any types of file. Files that are placed in the blob storage can be accessible through API, Microsoft Azure Storage Explorer, directly from the azure portal or from PowerShell. So if you have the need to archive files or share the access to the file to different environment or application that is located in different locations, then Blob Storage is a good candidate for you. For more detail, you may further check it out from this link https://docs.microsoft.com/en-us/azure/storage/common/storage-introduction#blob-storage.

So to get started on how to access Blob Storage from your code, firstly you need to retrieve the following packages from NuGet.

Microsoft.Azure.ConfigurationManager

Microsoft.Azure.KeyVault.Core

Microsoft.Azure.Storage.Blob

Microsoft.Azure.Storage.Common

Newtonsoft.Json

Once you have gotten the necessary packages, you need to define where is your blob storage located in your configuration file. But if you currently do not have an azure account, you may setup and run the Microsoft Azure Storage Emulator on your machine. Refer to this link https://docs.microsoft.com/en-us/azure/storage/common/storage-use-emulator for more information on how to set it up.

If you are using the Microsoft Azure Storage Emulator, define the following setting in the configuration file.

<add key="StorageConnectionString" value="UseDevelopmentStorage=true" />

Otherwise, you need to retrieve the connection string from the Azure Portal. The format of the connection string is as follows.

<add key="StorageConnectionString" value="DefaultEndpointsProtocol=https;AccountName=YourAzureBlobStorageName;AccountKey=YourAzureBlobStorageKey" />

To start using the packages retrieved from NuGet. Define the CloudStorageAccount instance based on the configuration defined above. This is to specify the location of the Azure Blob Storage.

[C#]

CloudStorageAccount cloudStorageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"));

[VB]

Dim cloudStorageAccount As CloudStorageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"))

With the CloudStorageAccount, use it to create the container. This is required before file can be placed into the Azure Blob Storage. Do take note that the container name must be lower case. For more detail about the container, you may check the following link https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blobs-introduction#blob-storage-resources.

[C#]

CloudBlobContainer cloudBlobContainer = cloudStorageAccount.CreateCloudBlobClient().GetContainerReference("containername");

cloudBlobContainer.CreateIfNotExists();

[VB]

Dim cloudBlobContainer As CloudBlobContainer = cloudStorageAccount.CreateCloudBlobClient().GetContainerReference("containername")

cloudBlobContainer.CreateIfNotExists()

After the creation of the container, it is now possible to upload file to the Azure Blob Storage. In the following demonstration, the file in the local machine will be used to upload.

[C#]

CloudBlockBlob cloudBlockBlob = cloudBlobContainer.GetBlockBlobReference("SampleFileInBlob.txt");

cloudBlockBlob.UploadFromFile(Path.Combine(Environment.CurrentDirectory, "SampleFile.txt"));

[VB]

Dim cloudBlockBlob As CloudBlockBlob = cloudBlobContainer.GetBlockBlobReference("SampleFileInBlob.txt")

cloudBlockBlob.UploadFromFile(Path.Combine(Environment.CurrentDirectory, "SampleFile.txt"))

Alternatively, the following demonstrate on how to retrieve the file from Azure Blob Storage and save it on local machine. 

[C#]

CloudBlockBlob cloudBlockBlob = cloudBlobContainer.GetBlockBlobReference("SampleFileInBlob.txt");

cloudBlockBlob.DownloadToFile(Path.Combine(Environment.CurrentDirectory, "SavedSampleFile.txt"), FileMode.Create);

[VB]

Dim cloudBlockBlob As CloudBlockBlob = cloudBlobContainer.GetBlockBlobReference("SampleFileInBlob.txt")

cloudBlockBlob.DownloadToFile(Path.Combine(Environment.CurrentDirectory, "SavedSampleFile.txt"), FileMode.Create)

Check out the sample code here https://1drv.ms/u/s!Aj2AA7hoIWHm03MBsAUCRtvATCYe.