With the symptoms as described in the question, and using Visual Studio 2013 (Update 4), I could see in the XML Schemas [sic] dialog that both DotNetConfig.xsd
and DotNetConfig40.xsd
were selected for use.
I'm using a .NET Framework 4.0 project.
The two XSD files conflict with each other, each defining the same elements, causing the warnings to be emitted.
These schema files are contained in the %programfiles(x86)%\Microsoft Visual Studio 12.0\xml\Schemas\
folder.
DotNetConfig.xsd
is in the 1033
sub-folder and appears to be the newer, more complete version.
No matter what settings I selected in XML Schemas, I could not deselect, or remove DotNetConfig40 nor DotNetConfig. I tried "Remove", and changing the Use parameter from "Use this schema" to "Automatic" and then "Do not use this schema".
No matter what was selected, for either file, when I would return to the dialog, both would be selected for use. I also tried the trick of moving to another row before pressing "OK" to no avail.
Finally, I renamed the DotNetConfig40.xsd
file to DotNetConfig40 DO NOT USE.xsd
to prevent it from being loaded. This immediately solved the problem.
I'm not pleased with having to do that, and worry if it'll have an undesired side effect with other projects. I'll update this post with my results.