The code from this chapter can be found on GitHub at https://github.com/PacktPublishing/C-8-and-.NET-Core-3-Projects-Using-Azure-Second-Edition.

It's probably worth spending some time exploring why you might choose to use Cosmos rather than one of the myriad other database engines. There are two questions here: why cloud, and why Cosmos specifically?

Because Cosmos DB is managed by Microsoft, transitioning to it means that there are suddenly some things that you don't need to worry about. For example, have you ever tried to configure SQL Server to fail over, or what about if you're located in the US and your customers are in Australia? Cosmos handles all these scenarios for you on a pay-as-you-go arrangement. Obviously, if you want your data replicated on...

Throughout this book, we will be using Azure as the cloud provider of choice. If you want to follow along and do not currently have an account, then you can create one at https://azure.microsoft.com/. At the time of writing, you can sign up for free and receive £150/$200 of credits for the first month.

Once you've signed up, visit https://portal.azure.com. Here, you can manage your Azure resources and check your balance.

Now that the resource is created, we can treat this database instance as though it was MongoDB. To start with, we'll need to launch the Data Explorer:

From here, we can select the following option to create a new collection:

As you can see, I've left the default values here. It's worth noting that Fixed (10 GB) is not the recommended value, and, in a production-grade application, you would very likely want to choose Unlimited. If you do so, then you will need to provide a partition key. I've left the throughput as the default 1000 Request Units per second (RU/s): this effectively allows you to pay for the performance that you need; the slower you go, the cheaper it is (and vice-versa)! Once created, you should be able to see your new collection:

The last thing to do is to navigate to the connection strings tab and copy...

When talking about using Cosmos DB in your application, one wonders how easy it will be to add this functionality to a new ASP.NET Core MVC application. The process is really easy. To start off, create a new project:

1. Name the project BugTracker:

2. Select the option to create an ASP.NET Core Web Application:

3. On the next screen, select the following options (referenced in the screenshot below):

4. Select ASP.NET Core 3.0 from the drop-down list.
5. Select Web Application (Model-View-Controller).
6. Uncheck the Enable Docker Support option. Finally, click on the OK button.
7. Click Create and your new ASP.NET Core MVC application will be created.

We will take a look at Docker and how...

In this section, we will have a look at how to read a list of work items from the MongoDB database and how to insert a new work item into the database (I use the term work item to refer to a task or a bug). This can be done by performing the following steps:

1. In the Models folder, create a new class called WorkItem, as shown in the following screenshot:

2. Add the following code to the WorkItem class. You will notice that Id is of the ObjectId type. This represents the unique identifier in the MongoDB document that gets created.

Take a look at the following code:

public class WorkItem 
{ 
    public ObjectId Id { get; set; } 
    public string Title { get; set; } 
    public string Description { get; set; } 
    public int Severity { get...

As mentioned earlier, Microsoft makes their money from Azure based on your usage. In order to avoid incurring costs, you should always clean up (that is, delete) resources that you no longer need. If, like me, you named your Cosmos DB instance bugtracker, then you can return to the Cosmos DB blade (you may have previously pinned this to your dashboard; otherwise, you should search for this) and select the instance.

Then simply select Delete Account:

As with many Azure resources, you have to complete a second step to confirm that you really want to delete the resource:

It may take a few seconds to complete, and after that, you're done.

There is still so much that you can learn when it comes to Cosmos DB and ASP.NET Core MVC. A single chapter is certainly not enough to cover it all. The days where databases sit on powerful, expensive servers that are housed in a rack in the office that only one guy has the keys to are very much numbered. This can be seen as good and bad: no-one can accidentally unplug or reboot the server, nor will a local power outage have any effect on it; however, you (or your employer) now pay for inefficient queries in pounds and pence (or dollars and cents).

In the next chapter, we will take a look at SignalR on Azure and how to create a real-time chat application.