Programmable SMS Quickstart for C# / .NET

With just a few lines of code, your .NET application can send and receive text messages with Twilio Programmable SMS.

This C# / .NET SMS Quickstart will teach you how to do this using our Communications REST API and the Twilio .NET helper library.

In this Quickstart, you will learn how to:

  1. Sign up for Twilio and get your first SMS-enabled Twilio phone number
  2. Set up your development environment to send and receive messages
  3. Send your first SMS
  4. Receive inbound text messages
  5. Reply to incoming messages with an SMS

Prefer to get started by watching a video? Check out our C# SMS Quickstart video on Youtube.

If you already have a Twilio account and an SMS-enabled Twilio phone number, you’re all set here! Feel free to jump to the next step.

Before you can send an SMS from C#, you'll need to sign up for a Twilio account or sign into your existing account and purchase an SMS-capable phone number.

If you don't currently own a Twilio phone number with SMS functionality, you'll need to purchase one.  After navigating to the Buy a Number page, check the "SMS" box and click "Search."

You’ll then see a list of available phone numbers and their capabilities. Find a number that suits your fancy and click "Buy" to add it to your account.

Now that you have a Twilio account and a programmable phone number, you can start writing some code! To make things even easier, we'll next install Twilio's official helper for .NET applications.

If you’ve gone through one of our other C# / .NET Quickstarts already and have .NET and the Twilio .NET helper library installed, you can skip this step and get straight to sending your first text message.

To send your first SMS, you’ll need to have .NET and the Twilio .NET package installed.

Install Visual Studio or .NET Core

If you have Visual Studio installed, you are ready to get going. If you plan to use .NET Core with an editor other than Visual Studio, you can check if you already have .NET Core installed on your machine by opening up a terminal and running the following command:

dotnet --version

You should see something like:

$ dotnet --version
2.1.4

If you don't have .NET Core already installed and will not be using Visual Studio, you can download .NET Core from Microsoft.

Install the Twilio .NET Package

The easiest way to install the library is using NuGet, the .NET package manager that lets you install the libraries you need.

Visual Studio

If you are using Visual Studio, select the "File" menu and choose "New" then "Project..." and select "Console App" (either .NET Core or .NET Framework will work).

Visual Studio New Console App

Then, select "Tools," "NuGet Package Manager," and "Package Manager Console" from the main menu in Visual Studio and type this command:

Install-Package Twilio
.NET Core Command Line

If you are using the dotnet command line tool, run these commands to create a new .NET project:

mkdir twilio-test
cd twilio-test
dotnet new console
dotnet add package Twilio

Send an Outbound SMS Message with C#

Now that we have .NET and the Twilio .NET library installed, we can send an outbound text message from the Twilio phone number we just purchased with a single API request. Open the file in your new project called Program.cs and type or paste in this code sample, replacing the template code that's already there.

Loading Code Samples...
Language
// Get the twilio-csharp library from twilio.com/docs/libraries/csharp
using System;
using Twilio;
using Twilio.Rest.Api.V2010.Account;
using Twilio.Types;

namespace YourNewConsoleApp
{
    class Example
    {
        static void Main(string[] args)
        {
            // Find your Account Sid and Auth Token at twilio.com/console
            const string accountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
            const string authToken = "your_auth_token";
            TwilioClient.Init(accountSid, authToken);

            var to = new PhoneNumber("+15017122661");
            var message = MessageResource.Create(
                to,
                from: new PhoneNumber("+15558675310"),
                body: "This is the ship that made the Kessel Run in fourteen parsecs?");

            Console.WriteLine(message.Sid);
        }
    }
}
This code creates a new instance of the Message resource and sends an HTTP POST to the Messages resource URI.
Send an SMS Using Twilio with C#

This code creates a new instance of the Message resource and sends an HTTP POST to the Messages resource URI.

You’ll need to edit this file a little more before your message will send:

Replace the placeholder credential values

Swap the placeholder values for accountSid and authToken with your personal Twilio credentials. Go to https://www.twilio.com/console and log in. On this page, you’ll find your unique Account SID and Auth Token, which you’ll need any time you send messages through the Twilio Client like this. You can reveal your auth token by clicking on the eyeball icon:

Edit Program.cs and replace the values for accountSid and authToken with your unique values.

Please note: it's okay to hardcode your credentials when getting started, but you should use configuration to keep them secret before deploying to production. ASP.NET applications should use the built-in configuration system for ASP.NET on the .NET Framework or ASP.NET Core. Other types of .NET applications could use environment variables.

Replace the "from" phone number

Remember that SMS-enabled phone number you bought just a few minutes ago? Go ahead and replace the existing from number with that one, making sure to use E.164 formatting:

[+][country code][phone number including area code]

Replace the "to" phone number

Replace the to phone number with your mobile phone number. This can be any phone number that can receive text messages, but it’s a good idea to test with your own phone, so you can see the magic happen! As above, you should use E.164 formatting for this value.

Save your changes and run this code either in Visual Studio or from your terminal:

dotnet run

That's it! In a few moments, you should receive an SMS from your Twilio number on your phone.

Are your customers in the U.S. or Canada? You can also send them MMS messages by adding just one line of code. Check out this guide to sending MMS to see how it's done.

If you are on a Twilio Trial account, your outgoing SMS messages are limited to phone numbers that you have verified with Twilio. Phone numbers can be verified via your Twilio Console's Verified Caller IDs.

Receive and Reply to Inbound SMS Messages with ASP.NET MVC

When your Twilio number receives an incoming message, Twilio will send an HTTP request to a server you control. This callback mechanism is known as a webhook.  When Twilio sends your application a request, it expects a response in the TwiML XML format telling it how to respond to the message. Let's see how we would build this in C# using ASP.NET MVC for .NET Framework 4.6.1. If you prefer using ASP.NET Core, check out this blog post. If you need to use ASP.NET Web API, we have an article for that, as well.

Create a New ASP.NET MVC Project in Visual Studio

In Visual Studio, select the "File" menu and choose "New" then "Project..." and select "ASP.NET Web Application (.NET Framework)."

Visual Studio New ASP.NET Web Application (.NET Framework)

Next, choose the "MVC" template.

Visual Studio New ASP.NET Web Application (.NET Framework) - MVC

Install the Twilio.AspNet.Mvc Package

Select "Tools," "NuGet Package Manager," and "Package Manager Console" from the main menu in Visual Studio and type the following command:

Install-Package Twilio.AspNet.Mvc -DependencyVersion HighestMinor

Create a New Controller

In the directory named Controllers, create a new Controller called SmsController.cs and use the following code to create a server that can handle incoming messages.

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// Code sample for ASP.NET MVC on .NET Framework 4.6.1+
// In Package Manager, run:
// Install-Package Twilio.AspNet.Mvc -DependencyVersion HighestMinor

using System.Web.Mvc;
using Twilio.AspNet.Mvc;
using Twilio.TwiML;

namespace YourNewWebProject.Controllers
{
    public class SmsController : TwilioController
    {
        [HttpPost]
        public TwiMLResult Index()
        {
            var messagingResponse = new MessagingResponse();
            messagingResponse.Message("The Robots are coming! Head for the hills!");

            return TwiML(messagingResponse);
        }
    }
}
When your phone number receives an incoming message, Twilio will send an HTTP request to your server. This code shows how your server should respond to reply with a text message (using TwiML).
Respond to an incoming text message

When your phone number receives an incoming message, Twilio will send an HTTP request to your server. This code shows how your server should respond to reply with a text message (using TwiML).

Run the project from Visual Studio. You should see the ASP.NET MVC home page running on localhost and a random port number.

Visual Studio New ASP.NET Web Application - Home page

You'll need to make your application accessible over the internet. While you can do that in any number of ways, we recommend a tool that provides an externally accessible URL called ngrok. We'll show you how to set that up next so your app can receive messages.

Allow Twilio to Talk to Your ASP.NET Application with ngrok

We’ve just built a small ASP.NET application to receive incoming messages. Before it will work, we need to make sure that Twilio can reach your application.

Most Twilio services use webhooks to communicate with your application. When Twilio receives an SMS, for example, it reaches out to a URL in your application for instructions on how to handle the message.

When you’re working on your ASP.NET application in your development environment, your app is only reachable by other programs on your computer, so Twilio won’t be able to talk to it. We need to solve this problem by making your application accessible over the internet.

While there are a lot of ways to do this, like deploying your application to Azure or AWS, you'll probably want a less laborious way to test your Twilio application. For a lightweight way to make your app available on the internet, we recommend a tool called ngrokNgrok listens on the same port that your local web server is running on and provides a unique URL on the ngrok.io domain, forwarding incoming requests to your local development environment. It works something like this:

How ngrok helps Twilio reach your local server

If you haven't done so already, install ngrok Extensions for Visual Studio. For more info on ngrok, including some great tips and tricks, check out this in-depth blog post.

After installing the Visual Studio extension, you will need to restart Visual Studio and reopen your project. Start your project again to bring up the home page. Then, while this is running, select "Start ngrok Tunnel" from the "Tools" menu.

Ngrok Extensions for Visual Studio

Ngrok Extensions for Visual Studio - running

Now we have a new external URL.

Configure Your Webhook URL

For Twilio to know where to look, you need to configure your Twilio phone number to call your webhook URL whenever a new message comes in.

  1. Log into Twilio.com and go to the Console's Numbers page.
  2. Click on your SMS-enabled phone number.
  3. Find the Messaging section. The default “CONFIGURE WITH” is what you’ll need: "Webhooks, TwiML, [etc.]".
  4. In the “A MESSAGE COMES IN” section, select "Webhook" and paste in your URL: in this quickstart step above, it would be: https://354f5b25.ngrok.io/sms - be sure to add /sms at the end, as this is the route to your SmsController class.

configure-phone-number

 Save your changes - you’re ready!

Test Your Application

Make sure you are running your project in Visual Studio, and your ngrok tunnel is running. If you restarted ngrok, you will have to update your webhook in the console to use the right URL.

With both of those servers running, we’re ready for the fun part - testing our new ASP.NET SMS application! 

Send an SMS from your mobile phone to your Twilio phone number that's configured with this webhook. You should see an HTTP request in your ngrok console. Your ASP.NET app will process the text message, and you’ll get your response back as an SMS.

Where to next?

Now that you know the basics of sending and receiving SMS and MMS text messages with C# and .NET, you might want to check out these resources.

Happy hacking!

Need some help?

We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.

Loading Code Samples...
// Get the twilio-csharp library from twilio.com/docs/libraries/csharp
using System;
using Twilio;
using Twilio.Rest.Api.V2010.Account;
using Twilio.Types;

namespace YourNewConsoleApp
{
    class Example
    {
        static void Main(string[] args)
        {
            // Find your Account Sid and Auth Token at twilio.com/console
            const string accountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
            const string authToken = "your_auth_token";
            TwilioClient.Init(accountSid, authToken);

            var to = new PhoneNumber("+15017122661");
            var message = MessageResource.Create(
                to,
                from: new PhoneNumber("+15558675310"),
                body: "This is the ship that made the Kessel Run in fourteen parsecs?");

            Console.WriteLine(message.Sid);
        }
    }
}
// Code sample for ASP.NET MVC on .NET Framework 4.6.1+
// In Package Manager, run:
// Install-Package Twilio.AspNet.Mvc -DependencyVersion HighestMinor

using System.Web.Mvc;
using Twilio.AspNet.Mvc;
using Twilio.TwiML;

namespace YourNewWebProject.Controllers
{
    public class SmsController : TwilioController
    {
        [HttpPost]
        public TwiMLResult Index()
        {
            var messagingResponse = new MessagingResponse();
            messagingResponse.Message("The Robots are coming! Head for the hills!");

            return TwiML(messagingResponse);
        }
    }
}