Recently I was trying to generate a simple Captcha for ASP.NET MVC. I looked at
MVC ReCaptcha, which is a great tool, but I didn't want a confusing ReCaptcha for simple form validation. My goal was to use something very simple to prevent SPAM, but at the same time provide a seamless enough experience to not scare off human users.
Next, I came across this article -
Simple CAPTCHA, Create your own in C#. It provides an excellent example on how to generate a simple Captcha. My next task was to convert this to ASP.NET MVC code (I used ASP.NET MVC 3.0). Documentation on this might be a little confusing, but the process ended up extremely simple.
The key that I learned here, is that you need to return
FileContentResult. Initially I tried returning
FileResult with no success.
public class CaptchaController : Controller
{
public ActionResult GetCaptcha()
{
var captcha = GetCaptchaImage();
var result = new FileContentResult(captcha, "image/png");
result.FileDownloadName = "captcha.png"; // optional
return result;
}
private Byte[] GetCaptchaImage()
{
// Code to generate your Captcha
// I used the logic from Raymund Macaalay's blog
// linked above
...
var oBytes = oMemoryStream.GetBuffer();
oMemoryStream.Close();
oMemoryStream.Dispose();
return oBytes;
}
}
Once you have this code, you can reference your image from views:
<img src="/Captcha/GetCaptcha/anything_you_want.png" />
One more thing to note, you can put any file name at the end. This part gets completely ignored by your controller (unless you modify it to take a parameter and do something with it). And that's it!
