Resolving DevExpress ASPX HtmlEditor error

Recently I got the following error when using the HTML editor control for ASP.NET.

Message: Invalid argument.
Line: 1147
Char: 3
Code: 0

This error only occurred only in Internet Explorer and only in our production environment, not with Firefox or Google Chrome, not in the test environment.

After some searching, I found out:

  • The issue occurs somewhat near the „_aspxCreateStyleSheet“ function.
  • A poster in the DevExpress forum experiences a similar issue when using too much style sheets.

Since I am using the ASP.NET „App_Themes“ folder with a lot of style sheets, I thought that this may be my issue, too.


By placing the following keys in the „appSettings“ section of the „web.config“ file on our production servers, I resolved the issue.

<add key=“DXEnableCallbackCompression“ value=“true“/>
<add key=“
DXEnableResourceCompression“ value=“true“/>
<add key=“DXEnableResourceMerging“ value=“true“/>
<add key=“DXEnableHtmlCompression“ value=“true“/>

I assume that the „DXEnableResourceCompression“ key probably merges multiple CSS files into one CSS, thus resolving the issue.

Please note that these „appSettings“ keys requires you to have a newer version of the libraries (9.2 if I recall correctly).