QuickStart: Build a Xamarin.Forms app with .NET SDK and Azure Cosmos DB's API for MongoDB

1. On Windows open a command prompt or on Mac open the terminal, create a new folder named git-samples, then close the window.

   md "C:\git-samples"
   

   mkdir '$home\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 };
  
  settings.RetryWrites = false;
  
  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 collection.

  public async Task CreateTask(MyTask task)
  {
      await TasksCollection.InsertOneAsync(task);
  }
  

• Update a task in a collection.

  public async Task UpdateTask(MyTask task)
  {
      await TasksCollection.ReplaceOneAsync(t => t.Id.Equals(task.Id), task);
  }
  

• Delete a task from a 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.

4. Remove &replicaSet=globaldb from the connection string. You will get a runtime error if you do not remove that value from the query string.

   Important

   You must remove the &replicaSet=globaldb key/value pair from the connection string's query string in order to avoid a runtime error.

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

Run the app

Visual Studio 2019

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 Azure portal monitors your Azure Cosmos DB account throughput, storage, availability, latency, and consistency. Charts for metrics associated with an Azure Cosmos DB Service Level Agreement (SLA) show the SLA value compared to actual performance. This suite of metrics makes monitoring your SLAs transparent.

To review metrics and SLAs:

1. Select Metrics in your Azure Cosmos DB account's navigation menu.

2. Select a tab such as Latency, and select a timeframe on the right. Compare the Actual and SLA lines on the charts.

   

3. Review the metrics on the other tabs.

Clean up resources

When you're done with your app and Azure Cosmos DB account, you can delete the Azure resources you created so you don't incur more charges. To delete the resources:

1. In the Azure portal Search bar, search for and select Resource groups.

2. From the list, select the resource group you created for this quickstart.

   

3. On the resource group Overview page, select Delete resource group.

   

4. In the next window, enter the name of the resource group to delete, and then select 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.

Trying to do capacity planning for a migration to Azure Cosmos DB? You can use information about your existing database cluster for capacity planning.

• If all you know is the number of vcores and servers in your existing database cluster, read about estimating request units using vCores or vCPUs
• If you know typical request rates for your current database workload, read about estimating request units using Azure Cosmos DB capacity planner