Add natural language understanding to your bot

APPLIES TO: yesSDK v4 no SDK v3

The ability to understand what your user means conversationally and contextually can be a difficult task, but can provide your bot a more natural conversation feel. Language Understanding, called LUIS, enables you to do just that so that your bot can recognize the intent of user messages, allow for more natural language from your user, and better direct the conversation flow. This topic walks you through adding LUIS to a flight booking application to recognize different intents and entities contained within user input.


About this sample

This core bot coding sample shows an example of an airport flight booking application. It uses a LUIS service to recognize the user input and return the top recognized LUIS intent.

After each processing of user input, DialogBot saves the current state of both UserState and ConversationState. Once all the required information has been gathered the coding sample creates a demo flight booking reservation. In this article we'll be covering the LUIS aspects of this sample. However, the general flow of the sample is shown below:

  • OnMembersAddedAsync is called when a new user is connected and displays a welcome card.
  • OnMessageActivityAsync is called for each user input received.

LUIS sample logic flow

The OnMessageActivityAsync module runs the appropriate dialog through the Run dialog extension method. Then the main dialog calls the LUIS helper to find the the top scoring user intent. If the top intent for the user input returns "BookFlight", the helper fills out information from the user that LUIS returned. After that, the nain dialog starts the BookingDialog, which acquires additional information as needed from the user such as:

  • Origin the originating city
  • TravelDate the date to book the flight
  • Destination the destination city

For details on the other aspects of the sample like dialogs or state, see Gather user input using a dialog prompt or Save user and conversation data.

Create a LUIS app in the LUIS portal

Sign in to the LUIS portal to create your own version of the sample LUIS app. You can create and manage your applications on My Apps.

  1. Select Import new app.
  2. Click Choose App file (JSON format)...
  3. Select FlightBooking.json file located in the CognitiveModels folder of the sample. In the Optional Name, enter FlightBooking. This file contains three intents: 'Book Flight', 'Cancel', and 'None'. We'll use these intents to understand what the user meant when they send a message to the bot.
  4. Train the app.
  5. Publish the app to production environment.

Why use entities

LUIS entities allow your bot to intelligently understand certain things or events that are different than the standard intents. This enables you to gather extra information from the user, which lets your bot respond more intelligently or possibly skip certain questions where it asks the user for that information. Along with definitions for the three LUIS intents 'Book Flight', 'Cancel', and 'None' the FlightBooking.json file also contains a set of entities such as 'From.Airport' and 'To.Airport'. These entities allow LUIS to detect and return additional information contained within the user's original input when they request a new travel booking.

For information on how entity information appears in a LUIS result, see Extract data from utterance text with intents and entities.

Obtain values to connect to your LUIS app

Once your LUIS app is published, you can access it from your bot. You will need to record several values to access your LUIS app from within your bot. You can retrieve that information using the LUIS portal.

Retrieve application information from the portal

The settings file (appsettings.json or .env) acts as the place to bring all service references together in one place. The information you retrieve will be added to this file in the next section.

  1. Select your published LUIS app from
  2. With your published LUIS app open, select the MANAGE tab. Manage LUIS app
  3. Select the Application Information tab on the left side, record the value shown for Application ID as <YOUR_APP_ID>.
  4. Select the Keys and Endpoints tab on the left side, record the value shown for Authoring Key as <YOUR_AUTHORING_KEY>.
  5. Scroll down to the end of the page, record the value shown for Region as <YOUR_REGION>.

Update the settings file

Add the information required to access your LUIS app including application id, authoring key, and region into the appsettings.json file. These are the values you saved previously from your published LUIS app. Note that the API host name should be in the format <your region>


  "MicrosoftAppId": "",
  "MicrosoftAppPassword": "",
  "LuisAppId": "",
  "LuisAPIKey": "",
  "LuisAPIHostName": ""

Configure your bot to use your LUIS app

Be sure that the Microsoft.Bot.Builder.AI.Luis NuGet package is installed for your project.

To connect to the LUIS service, the bot pulls the information you added above from the appsetting.json file. The FlightBookingRecognizer class contains code with your settings from the appsetting.json file and queries the LUIS service by calling RecognizeAsync method.


public class FlightBookingRecognizer : IRecognizer
    private readonly LuisRecognizer _recognizer;

    public FlightBookingRecognizer(IConfiguration configuration)
        var luisIsConfigured = !string.IsNullOrEmpty(configuration["LuisAppId"]) && !string.IsNullOrEmpty(configuration["LuisAPIKey"]) && !string.IsNullOrEmpty(configuration["LuisAPIHostName"]);
        if (luisIsConfigured)
            var luisApplication = new LuisApplication(
                "https://" + configuration["LuisAPIHostName"]);

            _recognizer = new LuisRecognizer(luisApplication);

    // Returns true if luis is configured in the appsettings.json and initialized.
    public virtual bool IsConfigured => _recognizer != null;

    public virtual async Task<RecognizerResult> RecognizeAsync(ITurnContext turnContext, CancellationToken cancellationToken)
        => await _recognizer.RecognizeAsync(turnContext, cancellationToken);

    public virtual async Task<T> RecognizeAsync<T>(ITurnContext turnContext, CancellationToken cancellationToken)
        where T : IRecognizerConvert, new()
        => await _recognizer.RecognizeAsync<T>(turnContext, cancellationToken);

The FlightBookingEx.cs contains the logic to extract From, To and TravelDate; it extends the partial class FlightBooking.cs used to store LUIS results when calling FlightBookingRecognizer.RecognizeAsync<FlightBooking> from the MainDialog.cs.


// Extends the partial FlightBooking class with methods and properties that simplify accessing entities in the luis results
public partial class FlightBooking
    public (string From, string Airport) FromEntities
            var fromValue = Entities?._instance?.From?.FirstOrDefault()?.Text;
            var fromAirportValue = Entities?.From?.FirstOrDefault()?.Airport?.FirstOrDefault()?.FirstOrDefault();
            return (fromValue, fromAirportValue);

    public (string To, string Airport) ToEntities
            var toValue = Entities?._instance?.To?.FirstOrDefault()?.Text;
            var toAirportValue = Entities?.To?.FirstOrDefault()?.Airport?.FirstOrDefault()?.FirstOrDefault();
            return (toValue, toAirportValue);

    // This value will be a TIMEX. And we are only interested in a Date so grab the first result and drop the Time part.
    // TIMEX is a format that represents DateTime expressions that include some ambiguity. e.g. missing a Year.
    public string TravelDate
        => Entities.datetime?.FirstOrDefault()?.Expressions.FirstOrDefault()?.Split('T')[0];

LUIS is now configured and connected for your bot.

Test the bot

Download and install the latest Bot Framework Emulator

  1. Run the sample locally on your machine. If you need instructions, refer to the readme file for either the C# Sample or JS Sample.

  2. In the emulator, type a message such as "travel to paris" or "going from paris to berlin". Use any utterance found in the file FlightBooking.json for training the intent "Book flight".

LUIS booking input

If the top intent returned from LUIS resolves to "Book flight" your bot will ask additional questions until it has enough information stored to create a travel booking. At that point it will return this booking information back to your user.

LUIS booking result

At this point the code bot logic will reset and you can continue to create additional bookings.

Next steps