An ASP.NET CAPTCHA Server Control

blog
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A few days ago, I found a really cool CAPTCHA ASP.NET code sample. I converted it to VB.NET and repackaged it as a full blown ASP.NET server control:

This is a companion discussion topic for the original blog entry at: http://www.codinghorror.com/blog/2004/10/an-aspnet-captcha-server-control.html
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Very nice!

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I developed one of these myself (in C#, however) and have it working on my site (link above).

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Brady, very cool, although I suspect that is very OCR-able due to the high contrast and lack of warping. Probably doesn’t matter since the effort bar has already been raised, but for the record :wink:

I made another small improvement: I am using a HttpHandler instead of a HttpModule. That way I don’t have to test every request for a page name… the handler only fires for that one page.

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There’s also a great MSDN article on this topic here:

http://msdn.microsoft.com/asp.net/using/building/web/default.aspx?pull=/library/en-us/dnaspp/html/hip_aspnet.asp

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The codeproject link doesn’t work any more. Is there an updated Url?

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Sure, that’s no problem. Scott Hanselman already included the CAPTCHA in his release of dasBlog as well.

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Looks like the MSDN URL has changed; I suspect it refers to this (very good) article:

<a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnaspp/html/hip_aspnet.asp">http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnaspp/html/hip_aspnet.asp</a>

This is based upon the .NET 1.x framework.

Regards, Matt

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For me, I have found that the control doesn’t work when it resides on a page that uses master pages. When the control is on a basic *.aspx page, it works fine. However, the site I want to use this with uses master pages. Can you help me to understand why that may be?? In laymen’s terms as well. I am not a code guru.

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I have solved my problem. There was a CSS conflict with my stylesheet and the styles applied to the DIV/SPAN elements within the control itself. It was also only an IE 6 bug as well. I stripped out all of the styles from your control and it worked with my stylesheet!

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Very nice! and very helpful. I shall use it in my .net projects.
thanks

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Nice work, Jefferson.

Why did you choose not to use it on codinghorror.com?

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The 2.0 project download on The Code Project is missing the CaptchaImage.aspx file.

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12w21w21

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One question and one comment…

First, great control! You saved me a ton of time. =)

Now, for the question…

I’m using your controlw ith a Template version of the Login control. Unfortunately, the control appears to not have any events that fire upon failure. I would to display a simple error to my user when they make a typo in the CAPTCHA.

Any thoughts or recommendations?

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Hi,

It is a great control and i am using it in a project.

The only problem is sometime the CAPTCHA image can not be displayed and i have to re-start IIS.

Please help.

Thanks

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anyone happen to have a C# version?
Tx…

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where is source code of this control…
and runtime files…

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Where’s the source code? The link is broken!

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There is an AJAX compatible version here: http://www.centrifugalbumblepuppy.com/posts/telerik-ajax-compatible-captcha-control.aspx