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Create a blob container with .NET

  • บทความ

Blobs in Azure Storage are organized into containers. Before you can upload a blob, you must first create a container. This article shows how to create containers with the Azure Storage client library for .NET.

Prerequisites

Set up your environment

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.

Install packages

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 using directives

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.

Create a client object

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.

Authorization

The authorization mechanism must have the necessary permissions to create a container. For authorization with Microsoft Entra ID (recommended), you need Azure RBAC built-in role Storage Blob Data Contributor or higher. To learn more, see the authorization guidance for Create Container (REST API).

About container naming

A container name must be a valid DNS name, as it forms part of the unique URI used to address the container or its blobs. Follow these rules when naming a container:

  • Container names can be between 3 and 63 characters long.
  • Container names must start with a letter or number, and can contain only lowercase letters, numbers, and the dash (-) character.
  • Consecutive dash characters aren't permitted in container names.

The URI for a container resource is formatted as follows:

https://my-account-name.blob.core.windows.net/my-container-name

Create a container

To create a container, call one of the following methods from the BlobServiceClient class:

You can also create a container using one of the following methods from the BlobContainerClient class:

These methods throw an exception if a container with the same name already exists.

Containers are created immediately beneath the storage account. It's not possible to nest one container beneath another.

The following example uses a BlobServiceClient object to create a container asynchronously:

//-------------------------------------------------
// Create a container
//-------------------------------------------------
private static async Task<BlobContainerClient> CreateSampleContainerAsync(BlobServiceClient blobServiceClient)
{
    // Name the sample container based on new GUID to ensure uniqueness.
    // The container name must be lowercase.
    string containerName = "container-" + Guid.NewGuid();

    try
    {
        // Create the container
        BlobContainerClient container = await blobServiceClient.CreateBlobContainerAsync(containerName);

        if (await container.ExistsAsync())
        {
            Console.WriteLine("Created container {0}", container.Name);
            return container;
        }
    }
    catch (RequestFailedException e)
    {
        Console.WriteLine("HTTP error code {0}: {1}",
                            e.Status, e.ErrorCode);
        Console.WriteLine(e.Message);
    }

    return null;
}

Create the root container

A root container serves as a default container for your storage account. Each storage account can have one root container, which must be named $root. The root container must be explicitly created or deleted.

You can reference a blob stored in the root container without including the root container name. The root container enables you to reference a blob at the top level of the storage account hierarchy. For example, you can reference a blob that is in the root container in the following manner:

https://myaccount.blob.core.windows.net/default.html

The following example creates the root container synchronously:

//-------------------------------------------------
// Create root container
//-------------------------------------------------
private static void CreateRootContainer(BlobServiceClient blobServiceClient)
{
    try
    {
        // Create the root container or handle the exception if it already exists
        BlobContainerClient container =  blobServiceClient.CreateBlobContainer("$root");

        if (container.Exists())
        {
            Console.WriteLine("Created root container.");
        }
    }
    catch (RequestFailedException e)
    {
        Console.WriteLine("HTTP error code {0}: {1}",
                            e.Status, e.ErrorCode);
        Console.WriteLine(e.Message);
    }
}

Resources

To learn more about creating a container using the Azure Blob Storage client library for .NET, see the following resources.

REST API operations

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 creating a container use the following REST API operation:

Client library resources

Related content

  • 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.