Manage container properties and metadata with .NET
Blob containers support system properties and user-defined metadata, in addition to the data they contain. This article shows how to manage system properties and user-defined metadata with the Azure Storage client library for .NET.
- Azure subscription - create one for free
- Azure storage account - create a storage account
- Latest .NET SDK for your operating system. Be sure to get the SDK and not the runtime.
If you don't have an existing project, this section shows you how to set up a project to work with the Azure Blob Storage client library for .NET. The steps include package installation, adding using
directives, and creating an authorized client object. For details, see Get started with Azure Blob Storage and .NET.
From your project directory, install packages for the Azure Blob Storage and Azure Identity client libraries using the dotnet add package
command. The Azure.Identity package is needed for passwordless connections to Azure services.
dotnet add package Azure.Storage.Blobs
dotnet add package Azure.Identity
Add these using
directives to the top of your code file:
using Azure.Identity;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using Azure.Storage.Blobs.Specialized;
Some code examples in this article might require additional using
directives.
To connect an app to Blob Storage, create an instance of BlobServiceClient. The following example shows how to create a client object using DefaultAzureCredential
for authorization:
public BlobServiceClient GetBlobServiceClient(string accountName)
{
BlobServiceClient client = new(
new Uri($"https://{accountName}.blob.core.windows.net"),
new DefaultAzureCredential());
return client;
}
You can register a service client for dependency injection in a .NET app.
You can also create client objects for specific containers or blobs. To learn more about creating and managing client objects, see Create and manage client objects that interact with data resources.
The authorization mechanism must have the necessary permissions to work with container properties or metadata. For authorization with Microsoft Entra ID (recommended), you need Azure RBAC built-in role Storage Blob Data Reader or higher for the get operations, and Storage Blob Data Contributor or higher for the set operations. To learn more, see the authorization guidance for Get Container Properties (REST API), Set Container Metadata (REST API), or Get Container Metadata (REST API).
System properties: System properties exist on each Blob storage resource. Some of them can be read or set, while others are read-only. Under the covers, some system properties correspond to certain standard HTTP headers. The Azure Storage client library for .NET maintains these properties for you.
User-defined metadata: User-defined metadata consists of one or more name-value pairs that you specify for a Blob storage resource. You can use metadata to store additional values with the resource. Metadata values are for your own purposes only, and do not affect how the resource behaves.
Metadata name/value pairs are valid HTTP headers and should adhere to all restrictions governing HTTP headers. For more information about metadata naming requirements, see Metadata names.
To retrieve container properties, call one of the following methods:
The following code example fetches a container's system properties and writes some property values to a console window:
private static async Task ReadContainerPropertiesAsync(BlobContainerClient container)
{
try
{
// Fetch some container properties and write out their values.
var properties = await container.GetPropertiesAsync();
Console.WriteLine($"Properties for container {container.Uri}");
Console.WriteLine($"Public access level: {properties.Value.PublicAccess}");
Console.WriteLine($"Last modified time in UTC: {properties.Value.LastModified}");
}
catch (RequestFailedException e)
{
Console.WriteLine($"HTTP error code {e.Status}: {e.ErrorCode}");
Console.WriteLine(e.Message);
Console.ReadLine();
}
}
You can specify metadata as one or more name-value pairs on a blob or container resource. To set metadata, add name-value pairs to an IDictionary object, and then call one of the following methods to write the values:
The following code example sets metadata on a container.
public static async Task AddContainerMetadataAsync(BlobContainerClient container)
{
try
{
IDictionary<string, string> metadata =
new Dictionary<string, string>();
// Add some metadata to the container.
metadata.Add("docType", "textDocuments");
metadata.Add("category", "guidance");
// Set the container's metadata.
await container.SetMetadataAsync(metadata);
}
catch (RequestFailedException e)
{
Console.WriteLine($"HTTP error code {e.Status}: {e.ErrorCode}");
Console.WriteLine(e.Message);
Console.ReadLine();
}
}
To retrieve metadata, call one of the following methods:
Then, read the values, as shown in the example below.
public static async Task ReadContainerMetadataAsync(BlobContainerClient container)
{
try
{
var properties = await container.GetPropertiesAsync();
// Enumerate the container's metadata.
Console.WriteLine("Container metadata:");
foreach (var metadataItem in properties.Value.Metadata)
{
Console.WriteLine($"\tKey: {metadataItem.Key}");
Console.WriteLine($"\tValue: {metadataItem.Value}");
}
}
catch (RequestFailedException e)
{
Console.WriteLine($"HTTP error code {e.Status}: {e.ErrorCode}");
Console.WriteLine(e.Message);
Console.ReadLine();
}
}
To learn more about setting and retrieving container properties and metadata using the Azure Blob Storage client library for .NET, see the following resources.
The Azure SDK for .NET contains libraries that build on top of the Azure REST API, allowing you to interact with REST API operations through familiar .NET paradigms. The client library methods for setting and retrieving properties and metadata use the following REST API operations:
- Get Container Properties (REST API)
- Set Container Metadata (REST API)
- Get Container Metadata (REST API)
The GetProperties
and GetPropertiesAsync
methods retrieve container properties and metadata by calling both the Get Blob Properties operation and the Get Blob Metadata operation.
- This article is part of the Blob Storage developer guide for .NET. To learn more, see the full list of developer guide articles at Build your .NET app.