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 follows: the file DotNetConfig.xsd has wrong (or not full) definition of the <startup> element. 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 as a non-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 10.0XmlSchemas directory (or %ProgramFiles(x86)%Microsoft Visual Studio 10.0XmlSchemas directory on 64-bit systems) with 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 course one can define the schema of all attributes or elements in a more detailed manner (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 contents of the catalog.xml file from the same directory, the schema of which is 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 interpreted by Visual Studio as files with the XSD schema described by one from above files.