How to escape the ampersand in WiX and MSI UI.

Someone asked recently how to use an ampersand (&) in the Product Name for their .wxs file.

Probably something like:

<Product Name="Stuff &amp; Stuff Demo" ...

The error message itself is pretty brutal but does pinpoint (to the exact character) the problem:

stuff.wxs(3) : error CNDL0104 : Not a valid source file; detail: An error
occurred while parsing EntityName. Line 3, position 27.

The error message is coming from the XML parser (we currently don’t try to trap those and print out friendlier error messages, not sure that is even possible) telling you that the the “entity” (things that start with an ampersand) name is invalid. The trick is to realize that ampersands are special characters in XML. Fortunately, this fact is pretty well documented all over the Internet. So the fix is easy:

<Product Name="Stuff &amp; Stuff Demo" ...

The follow up question was how to get an ampersand to show up in the UI. The issue is that if you have something like:

<Control Text="&amp;Print" ...

The control’s text is going to look like “Print”. For as long as I can remember, Windows dialogs have used used an ampersand to mark the accelerator key (or is it accessibility key?) . So hopefully it is no surprise that the Windows Installer chose to follow the same convention for their dialogs. Anyway, if you really wanted “&Print” to be the text of the control then you’d need to escape the ampersand like:

<Control Text="&amp;&amp;Print" ...

This is one of those cases where the special characters in one language (XML) also used represent special characters another language (MSI UI) end up complicating the escaping across the board. Fortunately, this doesn’t happen too often (and isn’t nearly as ugly as the escaping of XSL in Formatted text fields).