Azure Cosmos DB: Build a MongoDB API web app with .NET and the Azure portal

Azure Cosmos DB is Microsoft’s globally distributed multi-model database service. You can quickly create and query document, key/value, and graph databases, all of which benefit from the global distribution and horizontal scale capabilities at the core of Azure Cosmos DB.

This quick start demonstrates how to create an Azure Cosmos DB account, document database, and collection using the Azure portal. You'll then build and deploy a tasks list web app built on the MongoDB .NET driver.


If you don’t already have Visual Studio 2017 installed, you can download and use the free Visual Studio 2017 Community Edition. Make sure that you enable Azure development during the Visual Studio setup.

If you don't have an Azure subscription, create a free account before you begin.

Alternatively, you can Try Azure Cosmos DB for free without an Azure subscription, free of charge and commitments. Or you can use the Azure Cosmos DB Emulator for this tutorial with a connection string of


Create a database account

  1. In a new window, sign in to the Azure portal.
  2. In the left menu, click New, click Databases, and then under Azure Cosmos DB, click Create.

    Screen shot of the Azure portal, highlighting More Services, and Azure Cosmos DB

  3. In the New account blade, specify the desired configuration for the Azure Cosmos DB account.

    With Azure Cosmos DB, you can choose one of four programming models: Gremlin (graph), MongoDB, SQL, and Table (key-value).

    In this quick start we'll be programming against the MongoDB API so you'll choose MongoDB as you fill out the form. But if you have graph data for a social media app, document data from a catalog app, or key/value (table) data, realize that Azure Cosmos DB can provide a highly available, globally-distributed database service platform for all your mission-critical applications.

    Fill out the New account blade using the information in the table as a guide.

    Screen shot of the New Azure Cosmos DB blade

    Setting Suggested value Description
    ID Unique value A unique name you choose to identify the Azure Cosmos DB account. is appended to the ID you provide to create your URI, so use a unique but identifiable ID. The ID may contain only lowercase letters, numbers, and the '-' character, and must be between 3 and 50 characters.
    API MongoDB The API determines the type of account to create. Azure Cosmos DB provides five APIs to suits the needs of your application: SQL (document database), Gremlin (graph database), MongoDB (document database), Azure Table, and Cassandra, each which currently require a separate account.

    Select MongoDB because in this quickstart you are creating a document database that is queryable using MongoDB.

    Learn more about the MongoDB API
    Subscription Your subscription The Azure subscription that you want to use for the Azure Cosmos DB account.
    Resource Group The same value as ID The new resource group name for your account. For simplicity, you can use the same name as your ID.
    Location The region closest to your users The geographic location in which to host your Azure Cosmos DB account. Choose the location closest to your users to give them the fastest access to the data.
  4. Click Create to create the account.

  5. On the toolbar, click Notifications to monitor the deployment process.

    Deployment started notification

  6. When the deployment is complete, open the new account from the All Resources tile.

    Azure Cosmos DB account on the All Resources tile

Clone the sample application

Now let's clone a MongoDB API app from github, set the connection string, and run it. You'll see how easy it is to work with data programmatically.

  1. Open a git terminal window, such as git bash, and cd to a working directory.

  2. Run the following command to clone the sample repository.

    git clone
  3. Then open the solution file in Visual Studio.

Review the code

Let's make a quick review of what's happening in the app. Open the Dal.cs file under the DAL directory and you'll find that these lines of code create the Azure Cosmos DB resources.

  • Initialize the Mongo Client.

        MongoClientSettings settings = new MongoClientSettings();
        settings.Server = new MongoServerAddress(host, 10255);
        settings.UseSsl = true;
        settings.SslSettings = new SslSettings();
        settings.SslSettings.EnabledSslProtocols = SslProtocols.Tls12;
        MongoIdentity identity = new MongoInternalIdentity(dbName, userName);
        MongoIdentityEvidence evidence = new PasswordEvidence(password);
        settings.Credentials = new List<MongoCredential>()
            new MongoCredential("SCRAM-SHA-1", identity, evidence)
        MongoClient client = new MongoClient(settings);
  • Retrieve the database and the collection.

    private string dbName = "Tasks";
    private string collectionName = "TasksList";
    var database = client.GetDatabase(dbName);
    var todoTaskCollection = database.GetCollection<MyTask>(collectionName);
  • Retrieve all documents.

    collection.Find(new BsonDocument()).ToList();

Update your connection string

Now go back to the Azure portal to get your connection string information and copy it into the app.

  1. In the Azure portal, in your Azure Cosmos DB account, in the left navigation click Connection String, and then click Read-write Keys. You'll use the copy buttons on the right side of the screen to copy the Username, Password, and Host into the Dal.cs file in the next step.

  2. Open the Dal.cs file in the DAL directory.

  3. Copy your username value from the portal (using the copy button) and make it the value of the username in your Dal.cs file.

  4. Then copy your host value from the portal and make it the value of the host in your Dal.cs file.

  5. Finally copy your password value from the portal and make it the value of the password in your Dal.cs file.

You've now updated your app with all the info it needs to communicate with Azure Cosmos DB.

Run the web app

  1. In Visual Studio, right-click on the project in Solution Explorer and then click Manage NuGet Packages.

  2. In the NuGet Browse box, type MongoDB.Driver.

  3. From the results, install the MongoDB.Driver library. This installs the MongoDB.Driver package as well as all dependencies.

  4. Click CTRL + F5 to run the application. Your app displays in your browser.

  5. Click Create in the browser and create a few new tasks in your task list app.

Review SLAs in the Azure portal

The throughput, storage, availability, latency, and consistency of the resources in your account are monitored in the Azure portal. Let's take a quick look at these metrics.

  1. Click Metrics in the navigation menu.

    Metrics in the Azure portal

  2. Click through each of the tabs so you're aware of the metrics Azure Cosmos DB provides.

    Each chart that's associated with the Azure Cosmos DB Service Level Agreements (SLAs) provides a line that shows if any of the SLAs have been violated. Azure Cosmos DB makes monitoring your SLAs transparent with this suite of metrics.

    Azure Cosmos DB metrics suite

Clean up resources

If you're not going to continue to use this app, delete all resources created by this quickstart in the Azure portal with the following steps:

  1. From the left-hand menu in the Azure portal, click Resource groups and then click the name of the resource you created.
  2. On your resource group page, click Delete, type the name of the resource to delete in the text box, and then click Delete.

Next steps

In this quickstart, you've learned how to create an Azure Cosmos DB account and run a web app using the API for MongoDB. You can now import additional data to your Cosmos DB account.