Get started with Azure Cosmos DB for NoSQL using .NET

  • Article

APPLIES TO: NoSQL

This article shows you how to connect to Azure Cosmos DB for NoSQL using the .NET SDK. Once connected, you can perform operations on databases, containers, and items.

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Prerequisites

Set up your project

Create a new .NET application by using the dotnet new command with the console template.

dotnet new console

Import the Microsoft.Azure.Cosmos NuGet package using the dotnet add package command.

dotnet add package Microsoft.Azure.Cosmos

Build the project with the dotnet build command.

dotnet build

Connect to Azure Cosmos DB for NoSQL

To connect to the API for NoSQL of Azure Cosmos DB, create an instance of the CosmosClient class. This class is the starting point to perform all operations against databases.

To connect to your API for NoSQL account using Microsoft Entra, use a security principal. The exact type of principal will depend on where you host your application code. The table below serves as a quick reference guide.

Where the application runs Security principal
Local machine (developing and testing) User identity or service principal
Azure Managed identity
Servers or clients outside of Azure Service principal

Import Azure.Identity

The Azure.Identity NuGet package contains core authentication functionality that is shared among all Azure SDK libraries.

Import the Azure.Identity NuGet package using the dotnet add package command.

dotnet add package Azure.Identity

Rebuild the project with the dotnet build command.

dotnet build

In your code editor, add using directives for Azure.Core and Azure.Identity namespaces.

using Azure.Core;
using Azure.Identity;

Create CosmosClient with default credential implementation

If you're testing on a local machine, or your application will run on Azure services with direct support for managed identities, obtain an OAuth token by creating a DefaultAzureCredential instance.

For this example, we saved the instance in a variable of type TokenCredential as that's a more generic type that's reusable across SDKs.

// Credential class for testing on a local machine or Azure services
TokenCredential credential = new DefaultAzureCredential();

Create a new instance of the CosmosClient class with the COSMOS_ENDPOINT environment variable and the TokenCredential object as parameters.

// New instance of CosmosClient class using a connection string
using CosmosClient client = new(
    accountEndpoint: Environment.GetEnvironmentVariable("COSMOS_ENDPOINT")!,
    tokenCredential: credential
);

Create CosmosClient with a custom credential implementation

If you plan to deploy the application out of Azure, you can obtain an OAuth token by using other classes in the Azure.Identity client library for .NET. These other classes also derive from the TokenCredential class.

For this example, we create a ClientSecretCredential instance by using client and tenant identifiers, along with a client secret.

// Custom credential class for servers and clients outside of Azure
TokenCredential credential = new ClientSecretCredential(
    tenantId: Environment.GetEnvironmentVariable("AAD_TENANT_ID")!,
    clientId: Environment.GetEnvironmentVariable("AAD_CLIENT_ID")!,
    clientSecret: Environment.GetEnvironmentVariable("AAD_CLIENT_SECRET")!,
    options: new TokenCredentialOptions()
);

You can obtain the client ID, tenant ID, and client secret when you register an application in Azure Active Directory (AD). For more information about registering Azure AD applications, see Register an application with the Microsoft identity platform.

Create a new instance of the CosmosClient class with the COSMOS_ENDPOINT environment variable and the TokenCredential object as parameters.

// New instance of CosmosClient class using a connection string
using CosmosClient client = new(
    accountEndpoint: Environment.GetEnvironmentVariable("COSMOS_ENDPOINT")!,
    tokenCredential: credential
);

Build your application

As you build your application, your code will primarily interact with four types of resources:

  • The API for NoSQL account, which is the unique top-level namespace for your Azure Cosmos DB data.

  • Databases, which organize the containers in your account.

  • Containers, which contain a set of individual items in your database.

  • Items, which represent a JSON document in your container.

The following diagram shows the relationship between these resources.

Diagram of the Azure Cosmos DB hierarchy including accounts, databases, containers, and items.

Each type of resource is represented by one or more associated .NET classes. Here's a list of the most common classes:

Class Description
CosmosClient This class provides a client-side logical representation for the Azure Cosmos DB service. The client object is used to configure and execute requests against the service.
Database This class is a reference to a database that may, or may not, exist in the service yet. The database is validated server-side when you attempt to access it or perform an operation against it.
Container This class is a reference to a container that also may not exist in the service yet. The container is validated server-side when you attempt to work with it.

The following guides show you how to use each of these classes to build your application.

Guide Description
Create a database Create databases
Create a container Create containers
Read an item Point read a specific item
Query items Query multiple items

See also

Next steps

Create a database in Azure Cosmos DB for NoSQL using .NET