Send WhatsApp Group Messages in C# using Visual Studio 2019 - Complete Guide

Automate WhatsApp group messaging using the WhatsMate WA Gateway REST API

Posted on April 13, 2017   Share on Facebook Share on LinkedIn Share on Twitter Share on Google+

Last reviewed: February 13, 2026  

Automate WhatsApp Group Messaging with C# .NET Framework

Looking to integrate WhatsApp group messaging into your legacy .NET applications? This guide walks you through sending WhatsApp group messages using C# and the WhatsMate WA Gateway REST API with Visual Studio 2019. Perfect for .NET developers maintaining Windows applications, services, or enterprise solutions built on .NET Framework.

Note for Visual Studio 2022 users: If you’re using Visual Studio 2022 with modern .NET 6.0+, please refer to this updated tutorial for Visual Studio 2022 instead.

📋 Prerequisites

Before you begin, ensure you have:

  1. A WhatsMate WA Gateway Forever Green account - Required for group messaging API access
  2. Group setup - Create a WhatsApp group with a unique name and add the gateway
  3. Visual Studio 2019 - Community, Professional, or Enterprise edition
  4. .NET Framework - Version 4.5 or higher (legacy .NET Framework)
  5. Basic C# knowledge - Familiarity with Visual Studio 2019 and C# development

⚠️ Important: You need a Forever Green account to send messages to WhatsApp groups. The gateway must be added to your WhatsApp group before it can send messages. Sign up for a Forever Green account to enable group messaging capabilities.

📝 Step-by-Step Implementation

Follow these steps to send your first WhatsApp group message from a C# application in Visual Studio 2019:

1. Prepare Your WhatsApp Group

Before coding, set up your WhatsApp group:

  1. Create a new group in WhatsApp with a unique name (the API won’t work if the name isn’t unique)
  2. Add the secret gateway number to the group
  3. Send a “Hi” message (or any message) in the group from your personal WhatsApp account - this helps the gateway silently recognize the new group in the background

2. Copy the C# Template

Copy the following source code to the main class in your Console Application in Visual Studio:

3. Configure Key Parameters

Customize these essential parameters in the C# program:

  • Line 10: Replace YOUR_INSTANCE_ID_HERE with your WhatsApp gateway instance ID
  • Lines 11-12: Update YOUR_CLIENT_ID_HERE and YOUR_CLIENT_SECRET_HERE with your Forever Green Client ID and Secret
  • Line 19: Specify the group admin’s phone number (including country code, e.g., 12025550108)
  • Line 20: Provide your group name (must be unique)
  • Line 21: Enter your message content

4. Add Required Reference (Legacy .NET Framework)

For this legacy .NET Framework implementation, you need to add the System.Web.Extensions reference:

  1. Right-click on your project node in the Solution Explorer panel
  2. Choose “Add” → “Reference…”
  3. Select “Framework” on the left pane
  4. Find “System.Web.Extensions” in the middle pane and check the checkbox
  5. Click OK to add the reference

5. Build and Run

  1. Create a new Console Application in Visual Studio 2019
  2. Paste the code into your main class
  3. Build and run the application to send your WhatsApp group message

🔧 Common Use Cases

This C# .NET Framework integration is ideal for:

  • Legacy Windows applications - Add WhatsApp group notifications to existing WinForms or WPF applications built on .NET Framework
  • Enterprise maintenance projects - Integrate WhatsApp messaging into legacy business applications that still use .NET Framework
  • Migration projects - Add modern WhatsApp capabilities to older .NET Framework systems during migration planning
  • Compatibility requirements - Maintain WhatsApp integration for applications that must run on older Windows versions or .NET Framework environments

🚀 Get Started Today

Ready to integrate WhatsApp group messaging into your legacy C# .NET Framework applications? You’ll need a Forever Green account to access the group messaging API. Sign up for a Forever Green account and start sending group messages within minutes!

Next Steps: Once you’ve mastered basic group text messaging, explore advanced features like sending images or documents to WhatsApp groups through the WhatsMate WA Gateway API documentation.

Upgrade Recommendation: For new projects, consider using Visual Studio 2022 with .NET 6.0+ for modern .NET development with improved performance and features.