QuickStart: Build a MongoDB API Xamarin.Forms 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 quickstart demonstrates how to create an Azure Cosmos DB MongoDB API account, document database, and collection using the Azure portal. You'll then build a todo app Xamarin.Forms app by using the MongoDB .NET driver.

Prerequisites to run the sample app

To run the sample, you'll need Visual Studio or Visual Studio for Mac and a valid Azure CosmosDB account.

If you don't already have Visual Studio, download Visual Studio 2017 Community Edition with the Mobile development with .NET workload installed with setup.

If you prefer to work on a Mac, download Visual Studio for Mac and run the setup.

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

Create a database account

  1. In a new window, sign in to the Azure portal.
  2. In the left menu, click Create a resource, 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 MongoDB as the API and fill out your desired configuration for the Azure Cosmos DB account.

    • ID must be a unique name you wish to use to identify your Azure Cosmos DB account. It may only contain lower case letters, numbers, the '-' character, and must be between 3 and 50 characters.
    • Subscription is your Azure subscription. It will be filled out for you.
    • Resource Group is the resource group name for your Azure Cosmos DB account. Select Create New, then enter a new resource-group name for your account. For simplicity, you can use the same name as your ID.
    • Location is the geographic location where your Azure Cosmos DB instance is located. Choose the location closest to your users.

      Then click Create.

      The new account page for Azure Cosmos DB

  4. The account creation takes a few minutes. Wait for the portal to display the Congratulations! Your Azure Cosmos DB account with MongoDB API is ready page.

    The Azure portal Notifications pane

The sample described in this article is compatible with MongoDB.Driver version 2.6.1.

Clone the sample app

First, download the sample MongoDB API app from GitHub. It implements a todo app with MongoDB's document storage model.

  1. Open a command prompt, create a new folder named git-samples, then close the command prompt.

    md "C:\git-samples"
    
  2. Open a git terminal window, such as git bash, and use the cd command to change to the new folder to install the sample app.

    cd "C:\git-samples"
    
  3. Run the following command to clone the sample repository. This command creates a copy of the sample app on your computer.

    git clone https://github.com/Azure-Samples/azure-cosmos-db-mongodb-xamarin-getting-started.git
    

If you don't wish to use git, you can also download the project as a ZIP file

Review the code

This step is optional. If you're interested in learning how the database resources are created in the code, you can review the following snippets. Otherwise, you can skip ahead to Update your connection string.

The following snippets are all taken from the MongoService class, found at the following path: src/TaskList.Core/Services/MongoService.cs.

  • Initialize the Mongo Client.

    MongoClientSettings settings = MongoClientSettings.FromUrl(
        new MongoUrl(APIKeys.ConnectionString)
    );
    
    settings.SslSettings =
        new SslSettings() { EnabledSslProtocols = SslProtocols.Tls12 };
    
    MongoClient mongoClient = new MongoClient(settings);
    
  • Retrieve a reference to the database and collection. The MongoDB .NET SDK will automatically create both the database and collection if they do not already exist.

    string dbName = "MyTasks";
    string collectionName = "TaskList";
    
    var db = mongoClient.GetDatabase(dbName);
    
    var collectionSettings = new MongoCollectionSettings {
        ReadPreference = ReadPreference.Nearest
    };
    
    tasksCollection = db.GetCollection<MyTask>(collectionName, collectionSettings);
    
  • Retrieve all documents as a List.

    var allTasks = await TasksCollection
                    .Find(new BsonDocument())
                    .ToListAsync();
    
  • Query for particular documents.

    public async Task<List<MyTask>> GetIncompleteTasksDueBefore(DateTime date)
    {
        var tasks = await TasksCollection
                        .AsQueryable()
                        .Where(t => t.Complete == false)
                        .Where(t => t.DueDate < date)
                        .ToListAsync();
    
        return tasks;
    }
    
  • Create a task and insert it into the MongoDB collection.

    public async Task CreateTask(MyTask task)
    {
        await TasksCollection.InsertOneAsync(task);
    }
    
  • Update a task in a MongoDB collection.

    public async Task UpdateTask(MyTask task)
    {
        await TasksCollection.ReplaceOneAsync(t => t.Id.Equals(task.Id), task);
    }
    
  • Delete a task from a MongoDB collection.

    public async Task DeleteTask(MyTask task)
    {
        await TasksCollection.DeleteOneAsync(t => t.Id.Equals(task.Id));
    }
    

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 Primary Connection String in the next steps.

  2. Open the APIKeys.cs file in the Helpers directory of the TaskList.Core project.

  3. Copy your primary connection string value from the portal (using the copy button) and make it the value of the ConnectionString field in your APIKeys.cs file.

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

Run the app

Visual Studio 2017

  1. In Visual Studio, right-click on each project in Solution Explorer and then click Manage NuGet Packages.
  2. Click Restore all NuGet packages.
  3. Right click on the TaskList.Android and select Set as startup project.
  4. Press F5 to start debugging the application.
  5. If you want to run on iOS, first your machine is connected to a Mac (here are instructions on how to do so).
  6. Right click on TaskList.iOS project and select Set as startup project.
  7. Click F5 to start debugging the application.

Visual Studio for Mac

  1. In the platform dropdown list, select either TaskList.iOS or TaskList.Android, depending which platform you want to run on.
  2. Press cmd+Enter to start debugging the application.

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 with the following steps so you don't incur any charges:

  1. In the Azure portal, select Resource groups on the far left, and then select the resource group you created.

    If the left menu is collapsed, click Expand button to expand it.

    Metrics in the Azure portal

  2. In the new window select the resource group, and then click Delete resource group.

    Metrics in the Azure portal

  3. In the new window, type the name of the resource group to delete, and then click Delete.

Next steps

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