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Twilio Verify Phone Verification .NET Core C# Quickstart

Phone Verification is an important, high-confidence step in a registration flow to verify that a user has the device they claim to have. Adding Twilio Verify to your application to validate new accounts will greatly reduce your number of fraudulent registrations and protect future application users from having their numbers registered by scammers.

This quickstart guides you through creating an ASP.NET Core app that requires a Phone Verification step to create an account. Two channels of Phone Verification are demoed: SMS and Voice.

Ready to add Twilio Verify to a demo app and keep the bad actors away?

Sign Into (or Create) a Twilio Account

Either sign up for a free Twilio trial, or sign into an existing Twilio account.

Create a New Account Security Application

Once logged in, visit the Verify Console. Click on the red 'Create New Aplication' (or big red plus ('+') if you already created one) to create a new Verify application then name it something memorable.

verify create application

Twilio will redirect you to the Settings page next:

verify reveal keys

Click the eyeball icon to reveal your Production API Key, and copy it somewhere safe. You will use the API Key during the application setup step below.

Clone and Setup the Verification Application

Start by cloning our repository. Then, enter the directory and install dependencies:

git clone
cd account-security-csharp/src/AccountSecurity
dotnet restore
  1. Open the file appsettings.json
  2. Change AuthyApiKey to the API Key from the above step
        Enter the API Key from the Verify console and optionally change the port.

        Enter an Application API Key

        Enter the API Key from the Verify console and optionally change the port.

        Install and Launch SQL Server

        When a user registers with your application, a request is made to Twilio to add that user to your App, and a user_id is returned. In this demo, we'll store the returned user_id in an MSSQL database.

        On Windows, you can install the free SQL Server Express:

        On Linux or Mac, run it as a docker container:

        docker run -e 'ACCEPT_EULA=Y' -e 'SA_PASSWORD=yourStrong(!)Password' \
        -p 1433:1433 --name mssql -d microsoft/mssql-server-linux:latest

        Make sure your DefaultConnection connection string in appsettings.json is correct for your SQL Server installation. You may need to change the Server to localhost\\SQLEXPRESS if running MSSQL Server Express on Windows. Or, you may need to change the password if you selected a different one when starting your Docker container.

        Run the database migrations to get everything up to date:

        dotnet ef database update -v

        That's all the setup you'll need.

        Now, launch the application with:

        dotnet run --environment development

        Assuming your API Key is correctly entered, you'll soon get a message that the app is up!

        Use the .NET Core Twilio Verify Demo

        Keeping your phone at your side, visit the Phone Verification page of the demo at https://localhost:5001/verification/

        Enter a Country Code and Phone Number, then choose which channel to request verification over, 'SMS' or 'CALL' (Voice). Finally, hit the blue 'Request Verification' button and wait.

        Phone Verification by SMS or Voice

        You'll either receive a phone call or an SMS with the verification token. If you requested a phone call, as an additional security feature you may need to interact to proceed (enter a number on the phone keypad).


              Either way you requested the passcode, enter the token into the Verification entry form and click 'Verify Phone':

              Phone Verification Entry Box


                    And with that, your demo app is protected with Twilio's Phone Verification!

                    What's Next?

                    Your demo app is now keeping fraudulent users from registering with your business and polluting your database. Next, check out all of the variables and options available to you in the Phone Verification API Reference. Also, to protect your customers in an ongoing manner (with this same codebase) try the .NET Core Authy Two-Factor Authentication Quickstart.

                    After that, visit the Docs for more Account Security demos and tutorials and web applications using all of Twilio's products.

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                    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 by visiting our Twilio Community forums or browsing the Twilio tag on Stack Overflow.


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