A simple class library used for generating image captcha with audio dynamically without the need for external database or library.

Compatibility with .Net 4.0 and above versions.

This project is also available as a nuget package.
Install the latest package by entering the following command in Package Manager Console

Install-Package CaptchaGen

Visit this link for previous versions

Alternatively you can clone this repo and build it yourself and refer this project in your main project.

Generate captcha strings using CaptchaCodeFactory class. For example, the following snippet generates captcha string with 8 character length. Captcha string will contain alphanumeric characters generated with the help of RNGCryptoServiceProvider class to ensure randomness.

String captchaCode = CaptchaCodeFactory.GenerateCaptchaCode(8)

ImageFactory class generates the captcha image with the specified captcha string value. ImageFactory.GenerateImage(string) returns a Stream object that contains the image.

Following example snippet generates and serves the captcha image as an HttpResponseMessage

var imageStream = ImageFactory.GenerateImage(id);
imageStream.Position = 0;
HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContent(imageStream);
response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("image/jpeg");
return response;

AudioFactory class generates the audio data for a specified captcha string value. It utilizes SpeechSynthesizer class to generate the audio data. AudioFactory.GenerateAudio(string) returns a stream object that contains the audio data

The following example generates and serves the audio as a response for an incoming request

HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
var audioStream = AudioFactory.GenerateAudio(id);
audioStream.Position = 0;
response.Content = new StreamContent(audioStream);
response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("audio/wav");
return response;

You are welcome to contribute to the project by adding new features and improving the existing ones. Fork the project and create a pull request with your features.

MIT license.