# Send a notification to multiple channels --- Some situations call for notifications on multiple channels, whether due to the urgency or importance of the information, like emergency alerts, appointments canceled on short notice, or failed billing. This tutorial will take you through building a minimal .NET Core project which sends a message to multiple channels and reads the delivery reports. ## Prerequisites 1. [Infobip account](https://portal.infobip.com/login/?callback=https%3A%2F%2Fportal.infobip.com%2F). If you do not have one, you can easily [register](https://www.infobip.com/docs/essentials/getting-started/create-an-account). 2. [.NET SDK](https://learn.microsoft.com/en-us/dotnet/core/install/) installed. 3. [Node.js](https://nodejs.org/en/download/package-manager/) installed. ## Implementation ### Step 1: Use your API key and base URL [#step-1-use-your-api-key-and-base-url-implementation] Head to Infobip and copy the auto-generated API key and your base URL. If there is no option to copy the API key, the new API key can be created with the `message:send` scope. For more information, read about API scopes [here](https://www.infobip.com/docs/essentials/api-essentials/api-authorization). ### Step 2: Register Email single sender [#step-2-register-email-single-sender-implementation] You can use your email address to register a sender. Complete the first step of [Email onboarding](https://portal.infobip.com/login/?callback=https%3A%2F%2Fportal.infobip.com%2Fhomepage) on the Infobip account. Click the verification link sent to the provided email address. ### Step 3: Initiate a conversation via WhatsApp and Viber [#step-3-initiate-a-conversation-via-whatsapp-and-viber-implementation] Send the first message to your phone number from the first step in WhatsApp on the Infobip account and respond to the message in the WhatsApp app. Note that there is a 24-hour window for sending any message content. For more information, read about [initiating a conversation on WhatsApp](https://www.infobip.com/docs/api/channels/whatsapp). Do the same for Viber - send the first message from the Infobip account and respond using the Viber app. ### Step 4: Create an ASP.NET Core project [#step-4-create-an-asp-net-core-project-implementation] Either use your project or start from scratch with the [minimal API tutorial](https://learn.microsoft.com/en-us/aspnet/core/tutorials/min-web-api?view=aspnetcore-8.0&tabs=visual-studio-code). ### Step 5: Create a client for Infobip API [#step-5-create-a-client-for-infobip-api-implementation] First, create a client that can request the `messages-api` endpoint. For that purpose, define `HttpClient`. The copied API key will be added to the headers via `DefaultRequestHeaders.Authorization`, and the base URL will be set as `BaseAddress` in the following format: `https://your.api.infobip.com`: ```csharp var infobipClient = new HttpClient(); infobipClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("App", "paste-your-api-key-here"); infobipClient.BaseAddress = new Uri("https://paste-your-base-url-here"); ``` Next, define a new method that can invoke the messages endpoint via the previously defined `infobipClient`: ```csharp async Task SendAlerts() { var response = await infobipClient.PostAsJsonAsync("/messages-api/1/messages", new {}); Console.WriteLine("Messages response: {0}\n", response); } ``` ### Step 6: Build a request [#step-6-build-a-request-implementation] Valid request data is required to make a request. Define it for the Viber channel to start: ```csharp object BuildRequest() => new { Messages = new[] { new { Channel = "VIBER_BM", Sender = "DemoCompany", Destinations = new[] { new { To = "put-your-phone-number-here" } }, Content = new { Body = new { Text = "Hi, this is a friendly reminder that your appointment has been cancelled.", Type = "TEXT" } } } } }; ``` On the Infobip account, there is a page dedicated to all assigned Viber senders. During the free trial, you will have access to the assigned shared sender "DemoCompany" for testing Viber messages. Note For simplicity, an anonymous type object is used here. However, in production code, it is strongly recommended to define explicit classes. Edit the line with `infobipClient` to use the method defined earlier to build the request. ```csharp async Task SendAlerts() { var response = await infobipClient.PostAsJsonAsync("/messages-api/1/messages", BuildRequest()); Console.WriteLine("Messages response: {0}\n", response); } ``` ### Step 7: Add endpoint for sending alerts and trigger it [#step-7-add-endpoints-for-sending-alerts-and-trigger-it-implementation] Add an endpoint for invoking the method with the following logic: ```csharp app.MapPost("/alerts", async () => { await SendAlerts(); }) .WithName("PostAlerts") .WithOpenApi(); ``` After running the project, Swagger UI will open in your default browser, where you will be able to execute the `/alerts` endpoint: After execution, the message should be delivered to Viber shortly. If something did not go as planned, a response in the console will provide more detail. ### Step 8: Read delivery reports [#step-8-read-delivery-reports-implementation] You now have a working example of sending Viber messages, but you cannot be sure the messages were delivered. To receive delivery reports, set up a webhook endpoint that can trigger our app whenever delivery data is available. Find more details [here](https://www.infobip.com/docs/api/platform/messages-api/messages-api-status-reports/receive-messages-api-delivery-reports). To expose your local app via the public domain, use the [localtunnel CLI tool](https://github.com/localtunnel/localtunnel), which is built on Node.js. ```bash npm install -g localtunnel lt --port 5139 ``` The CLI will respond with a message skin: "Your URL is: https://hip-emus-car.loca.lt". Copy the URL and use it in the code below. Expand your request and include the "Webhooks" part with the new URL with the endpoint that you have built. For example, https://hip-emus-car.loca.lt/messages/webhook: ```csharp object BuildRequest() => new { Messages = new[] { new { Channel = "VIBER_BM", Sender = "DemoCompany", Destinations = new[] { new { To = "put-your-phone-number-here" } }, Content = new { Body = new { Text = "Hi, this is a friendly reminder that your appointment has been cancelled.", Type = "TEXT" } }, Webhooks = new { Delivery = new { Url = "https://hip-emus-car.loca.lt/messages/webhook" } } } } }; ``` Now create a new endpoint that will accept the `POST` request. Log the request in the console: ```csharp app.MapPost("/messages/webhook", (object request) => { Console.WriteLine("Webhook request: {0}\n", request); }) .WithName("PostWebhook") .WithOpenApi(); ``` When you execute the `/alerts` endpoint, you will see the delivery information provided via webhook in the console. ### Step 9: Defining other channels [#step-9-defining-other-channels-implementation] To specify additional channels, use a dictionary that associates each channel identifier with its corresponding sender. ```csharp var channelSenders = new Dictionary { { "SMS", "Info"}, { "VIBER_BM", "DemoCompany" }, { "WHATSAPP", "447860099299" }, }; ``` All assigned senders can be viewed on the Infobip account. Next, iterate over the dictionary and make a message request object for every item: ```csharp object BuildRequest() => new { Messages = channelSenders.Select(channelSender => new { Channel = channelSender.Key, Sender = channelSender.Value, Destinations = new[] { new { To = "put-your-phone-number-here" // for example: 447700900123 } }, Content = new { Body = new { Text = "Critical: Your payment process has failed. Please update your billing information urgently to avoid service interruption. Thank you.", Type = "TEXT" } }, Webhooks = new { Delivery = new { Url = "put-your-tunnelled-domain-with-webhook-endpoint" // for example: https://hip-emus-car.loca.lt/messages/webhook } } }) }; ``` Test the new implementation and execute the `/alerts` endpoint. You will now receive important messages across multiple channels simultaneously.