Visual Studio always selects the wrong xsd for App.config

Question

first of all, I have a .NET 4.0 application with this configuration:

<?xml version="1.0"?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
    </startup>
</configuration>

I had the same problem like the one in this question: app.config "Could not find schema information" after converting to Visual Studio 2010 / .Net 4.0 : The supportedRuntime element was not recognized by the editor, resulting in a hint.

I then followed the answer: I was in the app.config editor and went to the Properties window. There I selected the Schemas entry.

I removed the selection of the DotNetConfig.xsd and selected the DotNetConfig35.xsd instead, but VS always automatically adds the DotNetConfig.xsd again. Even if I set it explicitely to "do not use this schema" or even remove the schema from the list - it is automatically added to the list again and selected.

Because I now have two schemas selected that define the same elements I get a lot of warnings.

How can I change the schema to use the DotNetConfig35.xsd and NOT have the DotNetConfig.xsd automatically added again?

Answer 1

I interpret the problem as following: the file DotNetConfig.xsd has wrong (or not full) definition of the <startup> element. The line 230 of all DotNetConfig.xsd, DotNetConfig35.xsd, DotNetConfig30.xsd and DotNetConfig20.xsd files contains

<xs:element name="startup" vs:help="configuration/startup" />

On the other side Microsoft describes the startup settings schema not as empty element. So I suggest to replace the above line in DotNetConfig.xsd and in all DotNetConfigXX.xsd files from the %ProgramFiles%\Microsoft Visual Studio 10.0\Xml\Schemas directory (or %ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Xml\Schemas directory on 64-bit systems) to the following lines

<xs:element name="startup" vs:help="configuration/startup">
    <xs:complexType>
        <xs:choice minOccurs="1" maxOccurs="1">
            <xs:element name="requiredRuntime" vs:help="configuration/startup/requiredRuntime">
                <xs:complexType>
                    <xs:attribute name="version" type="xs:string" use="optional" />
                    <xs:attribute name="safemode" type="xs:boolean" use="optional" />
                </xs:complexType>
            </xs:element>
            <xs:element name="supportedRuntime" minOccurs="1" maxOccurs="unbounded" vs:help="configuration/startup/supportedRuntime">
                <xs:complexType>
                    <xs:attribute name="version" type="xs:string" use="optional" />
                    <xs:attribute name="sku" type="xs:string" use="optional" />
                </xs:complexType>
            </xs:element>
        </xs:choice>
        <xs:attribute name="useLegacyV2RuntimeActivationPolicy" type="xs:boolean" use="optional" />
        <!-- see http://msdn.microsoft.com/en-us/library/bbx34a2h.aspx -->
    </xs:complexType>
</xs:element>

After such modification and restarting of Visual Studio 2010 you will not have the warnings which you described. Of cause one can define the schema of all attributes or elements more detailed (especially if we find more detailed documentation of the <startup> section), but I want to describe the reason of the problem only and one way to fix it.

By the way the choice between DotNetConfig.xsd, DotNetConfig35.xsd and other DotNetConfigXX.xsd files will be done based on the contain of the catalog.xml file from the same directory, which schema described here. The standard version of the catalog.xml file contains the following lines

<Association extension="config" schema="%InstallRoot%/xml/schemas/dotNetConfig20.xsd" condition="starts-with($TargetFrameworkMoniker, '.NETFramework,Version=v2.')" />
<Association extension="config" schema="%InstallRoot%/xml/schemas/dotNetConfig30.xsd" condition="starts-with($TargetFrameworkMoniker, '.NETFramework,Version=v3.0')" />
<Association extension="config" schema="%InstallRoot%/xml/schemas/dotNetConfig35.xsd" condition="starts-with($TargetFrameworkMoniker, '.NETFramework,Version=v3.5')" />
<Association extension="config" schema="%InstallRoot%/xml/schemas/dotNetConfig.xsd"   condition="starts-with($TargetFrameworkMoniker, '.NETFramework,Version=v4.') or $TargetFrameworkMoniker = ''" />

So all files having .config extension will be interprets by Visual Studio as files with the XSD schema described by one from above files.

Answer 2

When I ran into this problem, the reason un-checking the schema didn't take turned out to be having multiple instances of Visual Studio open.

(I had VS2015 open with one project and VS2013 also open at the same time with a different project.)

Note, multiple versions of Visual Studio and switching back and forth on the same project/solution also seems to be how some issues with repeated schemas occurred in the first place.

Answer 3

This is an old post - but I just encountered the same problem.

The approach I took was the same one Ken Johnsrude suggested above - to create a new .xsd file:

http://w3stack.org/question/c-how-to-fix-error-could-not-find-schema-information-for-the-attributeelement-by-creating-schema/

1. MSVS > Open project app.config

2. XML > Create Schema

   This will create "app.xsd" in %TEMP%

    EXAMPLE: c:\users\paulsm\AppData\Local\Temp\app.xsd
   

3. Move app.xsd to project directory

4. App.Config, Right-click > Properties > Schemas > ... app.xsd > Use > Use this schema = YES