How to Send an RCS Message with Twilio and C# .NET

Time to read: 5 minutes

December 17, 2024
Written by
Alvin Lee
Contributor
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Reviewed by
Marius Obert
Twilion
Paul Kamp
Twilion

How to send an RCS message with C# .NET and Twilio

With the advent of Rich Communication Services (RCS), businesses are leveling up how they engage their customers. RCS brings a modern messaging experience that mirrors the interactive features of messaging apps that today’s consumers are accustomed to, while still delivering the reliability of SMS.

Apple devices also now support RCS as of the release of iOS 18. This has opened the door to new opportunities for integrating RCS.

In this tutorial, we’ll show you how to get started with RCS using Twilio and C# with .NET.

Twilio recently launched its public beta for RCS messaging. Join the public beta and start working with RCS today! Visit Twilio’s RCS Business Messaging page and click Get started. Your request should be approved within a few days.

Comparing RCS to SMS and WhatsApp

SMS is simple and sticky, meeting end users where they’re at. RCS enhances SMS by tacking on advanced features similar to those of modern messaging apps like WhatsApp. This brings a rich and interactive messaging experience to the consumer, and they don’t need to download a new app to get it. With RCS, businesses can leverage multimedia, verified sender profiles, and comprehensive engagement tracking support.

To see RCS in comparison with other messaging channels, see our Guide to Rich Communication Services: What Developers Need to Know.

Implementing RCS with Twilio and C# with .NET

If you’re ready to start sending messages via RCS, then Twilio is the place to get started. We’ll walk you through how to create an RCS sender and a messaging service. Then, we’ll show you how to send your first RCS message using C#.

Prerequisites

To get started, you will need the following:

  1. A Twilio account (sign up here).
  2. A Twilio phone number for sending SMS, as a fallback to your RCS service.
  3. A device capable of receiving RCS messages.
  4. The .NET framework installed on your development machine. 
dotnet -version # 8.0.404

Step 1: Create an RCS Sender

1. Log in to the Twilio Console.

2. Navigate to the Explore Products section and click RCS.
    • If RCS isn’t visible, you may need to request access here.

Screenshot of a web dashboard showing various communication services options with side navigation menu.

3. In the side panel, navigate to the Senders section.

4. Click Create new sender.

Web interface for managing email senders with sidebar options and a button to create a new sender

5. Provide a name (for example: “My First RCS Sender”). Click the continue button.

Dialog box for creating a new sender with display name and email, and instruction to add name and continue.

Step 2: Add Profile Information

Next, you’ll add profile information for your RCS sender. Use the following:

  • Sender display name: Choose a recognizable name for your sender. Usually, this is your brand name. For our example, we will use “My First RCS Sender”.
  • Description: Describe your brand. This description will be displayed just under your display name at the top of your user’s RCS interactions.
  • Border color: Keep in mind the minimum contrast ratio. For testing purposes, start with #000000 to keep it simple.
  • Logo: Your brand logo should meet the following requirements:
        • Dimensions: 224x224 pixels
        • File size: Max 50 KB
        • Image type: JPEG/JPG/PNG
        • For testing, you can use this example image: https://corn-lobster-7338.twil.io/assets/twiliodevs-logo-rcs.png
  • Banner: Your brand banner should meet the following requirements:
        • Dimensions: 1440x448 pixels
        • File size: Max 200KB
        • Image type: JPEG/JPG/PNG
        • For testing, you can use this example image: https://corn-lobster-7338.twil.io/assets/twiliodevs-banner-rcs.png
  • Contact Details - Phone number: A phone number associated with your RCS sender is required. Optionally, you can also add an email address.
  • Link to privacy policy and Link to terms of service: For testing purposes, you can enter links to arbitrary information here. When you begin building for production usage, make sure to create an RCS sender with real information about your business.
User filling out profile information and creating a Twilio sender profile on a computer screen.

Step 3: Test Your RCS Sender

  1. On the optional Test tab, click Add device to test this sender.
Confirmation page to test sender and add phone as a test device, including a sample message demo.
  • Enter the phone number of your RCS-capable device and click Invite.
  • You should receive an opt-in message from Twilio’s RCS agent on your device.
  • Confirm the opt-in on your device by selecting Make me a tester.
  • Check the dialog box in the Twilio Console, and send a test message.
Instructions on a phone and computer for confirming a test device and sending a first RCS message.
  • Celebrate—you’ve just sent your first RCS message!
Smartphone displaying an RCS message from a Twilio sender with a large hashtag symbol in the background.
  • Since this is just a test sender, click Save as draft and close.
Interface to create a sender in Twilio with phone number input and message preview on mobile screen.

Step 4: Create a Messaging Service

  1. In the Console, navigate to Messaging > Services.
  2. Click Create Messaging Service.
Screenshot of messaging services dashboard featuring a search bar and a Create Messaging Service button.
  • Give the new service a name (for example: “My RCS Service”) and click Create Messaging Service.
Web interface showing steps and fields for setting up a messaging service on a platform.
  • Add your RCS sender.
  • Click Add Sender, select RCS Sender.
Popup for adding a sender with RCS sender type selected on a messaging platform.
  • Add the RCS sender you just created.
Screenshot of a web interface for adding RCS senders with the option to select the RCS agent.
  • Add an SMS fallback sender by repeating the Add Sender process and selecting a phone number (or other SMS-capable sender). Then, click Step 3: Set up integration.
Messaging Service Sender Pool Configuration Screen

Step 5: (Optional) Set Up Webhook Integration

  1. Webhooks allow you to handle incoming messages in the same way as SMS or WhatsApp. Learn more in Twilio's docs about Incoming Message Webhooks.
  2. Use the Set Up Integration option to register a webhook. Feel free to reuse an existing one if available.
Screenshot of IBM Messaging Service integration setup with optional webhook configuration highlighted.

Step 6: Send Your First RCS Message with C#

1. Finish the wizard flow by clicking the white Skip setup button.

Screenshot of Meta Messenger Send API settings page with Skip the rest of the wizard highlighted.

2. Copy the Messaging Service SID (like MGe1fdfb207e9aa5b44f398b1094d88a8b) from the Console.

Twilio dashboard with steps to copy the messaging service SID under properties section in My SIP Services.

3. Retrieve your Account SID and Auth Token from the Twilio Console.

4. Create a new project with the .NET CLI. 

dotnet new console -o sendRCS
# The template "Console App" was created successfully.
#
# Processing post-creation actions...
# Restoring /home/user/SendRCS/SendRCS.csproj:
#  Determining projects to restore...
#  Restored /home/user/SendRCS/SendRCS.csproj (in 50 ms).
# Restore succeeded.

5. Create a file in your project folder called .env. Add the credentials from the previous steps, so that your file looks like this: 

MESSAGING_SERVICE_SID=replace-with-your-messaging-service-sid
ACCOUNT_SID=replace-with-your-twilio-account-sid
AUTH_TOKEN=replace-with-your-twilio-auth-token

6. Add the dependency packages you will use in your application code. 

dotnet add package DotNetEnv
dotnet add package Twilio

7. Edit the auto-generated Program.cs file to look like this: 

using System;
using Twilio;
using Twilio.Rest.Api.V2010.Account;
using System.Threading.Tasks;
using DotNetEnv;

class Program {
  public static async Task Main(string[] args) {
    DotNetEnv.Env.Load();

    TwilioClient.Init(
      Environment.GetEnvironmentVariable("ACCOUNT_SID"),
      Environment.GetEnvironmentVariable("AUTH_TOKEN")
    );

    var ms = Environment.GetEnvironmentVariable("MESSAGING_SERVICE_SID");
    var toPhone = new Twilio.Types.PhoneNumber("+<INSERT THE NUMBER USED AS TEST DEVICE>"); 

    var message = await MessageResource.CreateAsync(
      body: "This RCS message contains an image!",
      messagingServiceSid: ms,
      to: toPhone,
      mediaUrl: new List<Uri> { new Uri(
        "https://pbs.twimg.com/media/GZbs3vZWAAAwqVX?format=jpg&name=medium"
      ) }
    );

    Console.WriteLine(message.Body);
  }
}

8. Build and run the application. 

dotnet build
#  Determining projects to restore...
#  All projects are up-to-date for restore.
#  SendRCS -> /home/user/SendRCS/bin/Debug/net8.0/SendRCS.dll
#
# Build succeeded.
#    0 Warning(s)
#    0 Error(s)
#
# Time Elapsed 00:00:01.17
dotnet run

9. See the result on your RCS-enabled device.

Phone screen displaying an RCS message received from a Twilio sender along with Twilio and RCS logos.

Explore Advanced RCS Features

You have successfully sent an RCS message using C# with .NET. Nice work!

When businesses use RCS to engage their customers, they get access to new avenues for engagement and interactivity. To continue leveling up your skills, check out some of the other things you can do in conjunction with RCS:

  • Use the Content Template Builder to create rich message content which you can use across various channels, including SMS, WhatsApp, and RCS.
  • Explore the Programmable Messaging Logs to see message statuses and troubleshoot any errors.
  • Work with Twilio Verify to send OTP codes with RCS. Twilio Verify lets you deliver secure and engaging one-time passwords to your users.

Twilio is continuously enhancing its RCS capabilities. This includes new features like failover for undelivered messages and quick reply buttons. There’s more coming, so stay tuned for updates!

Modern businesses are using RCS to transform their customer engagement approach. With RCS, you get the reliability of SMS with the interactive features that end users expect from the messaging apps they know and love.

We can’t wait to see what you build!

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