Send PDF Files over WhatsApp in C#/.NET (Visual Studio 2019) - Complete Guide

Automate WhatsApp PDF document sharing using the WhatsMate WA Gateway REST API

Posted on January 17, 2018   Share on Facebook Share on LinkedIn Share on Twitter Share on Google+

Last reviewed: February 12, 2026  

Automate WhatsApp PDF Sharing with C#/.NET and Visual Studio 2019

⚠️ Visual Studio 2019 Notice: This guide uses Visual Studio 2019 with legacy .NET libraries. For new projects, we recommend using Visual Studio 2022 with modern C#/.NET for better performance, security, and modern features.

Looking to automate WhatsApp PDF document sharing from legacy C#/.NET applications using Visual Studio 2019? This guide walks you through sending PDF files to WhatsApp users using C# with Visual Studio 2019 and the WhatsMate WA Gateway REST API. Perfect for maintaining legacy .NET applications that require WhatsApp document delivery capabilities.

📋 Prerequisites

Before you begin, ensure you have:

  1. A WhatsMate WA Gateway account - Required for API access
  2. Recipient registration - Each recipient must register with the Gateway first
  3. Visual Studio 2019 - Legacy .NET development environment
  4. PDF file ready - Have the PDF file you want to send available locally
  5. Legacy .NET libraries - This version uses System.Web.Script.Serialization (requires System.Web.Extensions reference)

⚠️ Important: Recipients must register with the WhatsMate WA Gateway before they can receive messages. Unregistered users will not receive any messages from the Gateway. Registration instructions are available on the official WhatsMate site.

📝 Step-by-Step Implementation

Follow these steps to send your first PDF file to a WhatsApp user from a legacy C# application using Visual Studio 2019:

1. Copy the C# Code Template

Start by copying the following source code into your C# file:

2. Configure a few Parameters

Customize these key parameters in the C# code:

  • Line 10: Replace YOUR_INSTANCE_ID with your WhatsApp gateway instance ID
  • Lines 11-12: Update YOUR_CLIENT_ID_HERE and YOUR_CLIENT_SECRET_HERE with your Client ID and Secret
  • Line 20: Replace 12025550105 with the target phone number (including the country code)
  • Line 22: Replace C:\\TEMP\\subwaymap.pdf with the path to your PDF file
  • Line 23: Replace anyname.pdf with your preferred filename for the recipient
  • Line 24: Replace You will find the map handy. with your desired caption

3. Add Required Reference

In Visual Studio 2019, ensure you have the System.Web.Extensions reference added:

  1. Right-click your project → Add Reference
  2. Go to Assemblies → Framework
  3. Check System.Web.Extensions
  4. Click OK

4. Send Your PDF

Build and run your C# application in Visual Studio 2019 to deliver your PDF to WhatsApp:

  1. Press F5 to build and run in debug mode
  2. Or use Ctrl+F5 to run without debugging
  3. Check the console output for success confirmation

🔧 Common Use Cases

This legacy automation approach is ideal for:

  • Maintaining legacy Windows applications - Send PDF reports to WhatsApp from older Windows Forms or WPF apps
  • Legacy ASP.NET web applications - Integrate WhatsApp PDF sharing into older ASP.NET web apps
  • Legacy system integration - Connect older .NET Framework applications to modern WhatsApp messaging
  • Business reporting for legacy systems - Automatically send PDF reports from existing .NET Framework applications
  • Document automation for legacy workflows - Generate and send PDF documents from legacy Office automation systems

🚀 Get Started Today

Ready to automate your PDF sharing over WhatsApp with legacy C#/.NET and Visual Studio 2019? You’ll need a trial account to access the API. Sign up for a 2-week trial and start sending PDF documents within minutes!

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