How to send messages to a WhatsApp group in C# using Visual Studio 2019

Using the WhatsMate WA Gateway REST API

This article shows you how to send a message to a WhatsApp group in Microsoft’s .net language: C# using Visual Studio 2019.

If you are using Visual Studio 2022, please read this tutorial instead.

You MUST obtain the secret gateway number by signing up for a Forever Green account before you can send a message to a WhatsApp group. Instructions are available on the official site.

To send a WhatsApp group message in C#, do this:

  1. Create a new group with a unique name. The API won’t work if it’s not unique.
    • Create a new WhatsApp group

  2. Add the secret gateway to the group.
    • Name the WhatsApp group

  3. Say “Hi” to the group to let the gateway recognize the new group.
  4. Copy the following source code to the main class in your Console Application in Visual Studio.
  5. Customize the TODO lines in the C# program:
    • Specify your gateway instance ID on line 10.
    • Specify your Client ID and Client secret on lines 10 and 11.
    • Specify the group admin number (i.e. your WhatsApp number including the country code) on line 19.
    • Specify the group name (e.g. Happy Club) on line 20.
    • Specify the content of the message on line 21.
  6. Add the reference “System.Web.Extensions” by doing this:
    • Right-click on your project node in the Solution Explorer panel.
    • Choose “Add” -> “Reference…”
    • Choose “Framework” on the left pane.
    • Look for “System.Web.Extensions” in the middle pane. Check the checkbox in front of it.
    • Click OK.
  7. Build and run the application in Visual Studio.

As mentioned at the beginning of this tutorial, you will need a trial account to call the above API. Go sign up now.

Happy coding :)