Appointment Reminders with C# and ASP.NET MVC

Ready to implement appointment reminders in your application? Here's how it works:

1. An administrator creates an appointment for a future date and time, and stores a customer's phone number in the database for that appointment
2. A background process checks the database on a regular interval, looking for appointments that require a reminder to be sent out
3. At a configured time in advance of the appointment, an SMS reminder is sent out to the customer to remind them of their appointment

Check out how Yelp uses SMS to confirm restaurant reservations for diners.

Building Blocks

Here are the technologies we'll use to get this done:

• ASP.NET MVC to create a database-driven web application
• The Messages Resource from Twilio's REST API to send text messages
• Hangfire to help us schedule and execute background tasks on a recurring basis

In this tutorial, we'll point out key snippets of code that make this application work. Check out the project README on GitHub to see how to run the code yourself.

How To Read This Tutorial

To implement appointment reminders, we will be working through a series of user stories that describe how to fully implement appointment reminders in a web application. We'll walk through the code required to satisfy each story, and explore what we needed to add on each step.

All this can be done with the help of Twilio in under half an hour.

Creating an Appointment

As a user, I want to create an appointment with a name, guest phone numbers, and a time in the future.

In order to build an automated appointment reminder application, we probably should start with an appointment. This story requires that we create a bit of UI and a model object to create and save a new Appointment in our system. At a high level, here's what we will need to add:

• A form to enter details about the appointment
• A route and controller function on the server to render the form
• A route and controller function on the server to handle the form POST request
• A persistent Appointment model object to store information about the user

Alright, so we know what we need to create a new appointment. Now let's start by looking at the model, where we decide what information we want to store with the appointment.

Appointment Model

The appointment model is fairly straightforward, but since humans will be interacting with it let's make sure we add some data validation.

Our application relies on ASP.NET Data Annotations. In our case, we only want to validate that some fields are required. To accomplish this we'll use [Required] data annotation.

By default, ASP.NET MVC displays the property name when rendering a control. In our example those property names can be Name or PhoneNumber. For rendering Name there shouldn't be any problem. But for PhoneNumber we might want to display something nicer, like "Phone Number". For this kind of scenario we can use another data annotation: [Display(Name = "Phone Number")].

For validating the contents of the PhoneNumber field, we're using [Phone] data annotation, which confirms user-entered phone numbers conform loosely to E.164 formatting standards.

New Appointment Form

When we create a new appointment, we need a guest name, a phone number and a time. By using HTML Helper classes we can bind the form to the model object. Those helpers will generate the necessary HTML markup that will create a new appointment on submit.

Interacting with Appointments

As a user, I want to view a list of all future appointments, and be able to delete those appointments.

If you're an organization that handles a lot of appointments, you probably want to be able to view and manage them in a single interface. That's what we'll tackle in this user story. We'll create a UI to:

• Show all appointments
• Delete individual appoinments

We know what interactions we want to implement, so let's look first at how to list all upcoming Appointments.

Getting a List of Appointments

At the controller level, we'll get a list of all the appointments in the database and render them with a view. We also add a prompt if there aren't any appointments, so the admin user can create one.

That's how we return the list of appointments, now we need to render them. Let's look at the Appointments template for that.

Sending Reminders

As an appointment system, I want to notify a user via SMS an arbitrary interval before a future appointment.

There are a lot of ways to build this part of our application, but no matter how you implement it there should be two moving parts:

• A script that checks the database for any appointment that is upcoming, and then sends a SMS.
• A worker that runs that script continuously.

Let's take a look at how we decided to implement the latter with Hangfire.

Working with Hangfire

If you've never used a job scheduler before, you may want to check out this post by Scott Hanselman that shows a few ways to run background tasks in ASP.NET MVC. We decided to use Hangfire because of its simplicity. If you have a better way to schedule jobs in ASP.NET MVC please let us know.

Hangfire needs a backend of some kind to queue the upcoming jobs. In this implementation, we're using SQL Server Database, but it's possible to use a different data store. You can check their documentation for further details.

Now that we have included Hangfire dependencies into the project, let's take a look at how to configure it to use it in our appointment reminders application.

Hangfire Configuration Class

We created a class named Hangfire to configure our job scheduler. This class defines two static methods:

1. ConfigureHangfire to set initialization parameters for the job scheduler.
2. InitialzeJobs to specify which recurring jobs should be run, and how often they should run.

That's it for the configuration. Let's take a quick look next at how we start up the job scheduler.

Starting the Job Scheduler

This ASP.NET MVC project is an OWIN-based application, which allows us to create a startup class to run any custom initialization logic required in our application. This is the preferred location to start Hangfire - check out their configuration docs for more information.

Now that we've started the job scheduler, let's take a look at the logic that gets executed when our job runs.

Notification Background Job

In this class, we define a method called Execute which is called every minute by Hangfire. Every time the job runs, we need to:

1. Get a list of upcoming appointments that require notifications to be sent out
2. Use Twilio to send appointment reminders via SMS

The AppointmentsFinder class queries our SQL Server database to find all the appointments whose date and time are coming up soon. For each of those appointments, we'll use the Twilio REST API to send out a formatted message.

Now that we are retrieving a list of upcoming Appointments, let's take a look next at how we use Twilio to send SMS notifications.

Twilio REST API Request

This class is responsible for reading our Twilio account credentials from Web.config, and using the Twilio REST API to actually send out a notification to our users. We also need a Twilio number to use as the sender for the text message. Actually sending the message is a single line of code!

Where to Next?

And with a little code and a dash of configuration, we're ready to get automated appointment reminders firing in our application. Good work!

If you are a C# developer working with Twilio, you might want to check out other tutorials:

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