About Recaptcha for .NET
Recaptcha for .NET is a library that allows a developer to easily integrate Google's Recaptcha service (the most popular captcha control) in an ASP.NET Web Forms or ASP.NET MVC web application.

The library is one of the most solid captcha libraries with best documentation. Unlike most other recaptcha libraries, it supports both ASP.NET Web Forms and ASP.NET MVC.
Features
The primary features of the library are:
- Renders recaptcha control with appropriate options.
- Verifies user's answer to recaptcha's challenge.
- Supports ASP.NET 4.0 and 4.5.
- Compatible with ASP.NET MVC 2, 3, and 4.
What's New?
- Verify user's answer to recpatcha's challenge asynchronously and take advantage of the new await keyword.
- Manually set recpatcha control's language property. By default, it uses current UI culture's language.
Documentation
Please go through the step-by-step
documentation that will guide you through the entire process of installing and using Recaptcha for .NET.
Source Code
Of course, Recaptcha for .NET is open source. Go to the
Source Control tab and navigate through the source code of the library. It also contains some sample projects in the Samples directory.
Issues and Bugs
Every effort has been made to ensure the quality of Recaptcha for .NET. However, if you find any issue or bug in library then please log them in the
Issue Tracker on CodePlex.