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The Community Blog is a personal opinion of community members and by no means the official standpoint of DNN Corp or DNN Platform. This is a place to express personal thoughts about DNNPlatform, the community and its ecosystem. Do you have useful information that you would like to share with the DNN Community in a featured article or blog? If so, please contact .

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DNN8 DnnImageHandler.ashx 404

With DNN8 a new Image Handler was introduced to provide loading/sizing of images of various sizes. In previous releases the ProfilePic.ashx implementation always looked like it was supposed to do allow for this, but never actually allowed you to resize images in a meaningful way.

The handler in DNN8 allows for this, but I was having a problem as I started using this method in the DNNChat module (new release coming in the next few days) but when I installed it on the images were failing to load, and then ended up throwing 404 messages. I wasn't quite sure what the cause was, but decided to check the AUM_ settings in the hostsettings table. In my install there I found a setting AUM_DoNotRedirectUrlRegex that had the following value:


That is NOT the "Default" setting for that, it is something I have overridden over the years, and as the "default" value, hard coded in DNN, has changed, my version hasn't been kept in sync. 

With the URL rewriting that was introduced in DNN 7.1, there are hard coded values for that setting, and other "AUM_" settings in the Code for DNN, the default behavior in DNN is to use these hard coded settings, and if any settings are found in the HostSettings table, they will override the hard coded values. Here's the default setting hard coded in DNN right now:


In my case, I don't have the string '|\.ashx|' in the setting, so DNN doesn't know to let all ASHX requests get processed without URL rewriting. In order to fix this I needed to address this. There are a couple of days, I could have just executed this SQL:

update hostsettings 

set settingvalue=settingvalue + '|\.ashx'

where settingname ='AUM_DoNotRedirectUrlRegex'

That would have added the ASHX reference that I needed in this case, but I would be missing other "Defaults", so to correct for this I decided to reset the setting using the default values, but, because my DNNChat module uses SignalR I do need to add '|\SignalR' to the end of the setting, so that DNN won't jack with the /signalr/hubs/ calls. I also had a value in there for a custom module that I wanted to add back in. Here's the SQL I ran on my database to clean this up. 

update hostsettings 

set settingvalue='(\.axd)|/Rss\.aspx|/SiteMap\.aspx|\.ashx|/LinkClick\.aspx|/Providers/|

where settingname ='AUM_DoNotRedirectUrlRegex'

Hopefully this will help you if you ever need to start getting into URL overrides in DNN.

DISCLAIMER: Always back up your database and files before performing any maintenance. I'm not responsible if you screw up your website/database. 


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