Question

We are deploying our ASP.Net MVC application to a windows 2008 R2 server, running IIS 7.5.

After deployment, we get this error in the event log (we also get an email) :
"Unrecognized element ‘providerOption’" on line x in c:\wwwroot\web.config
which is:

<providerOption name="CompilerVersion" value="v3.5"> 

located in the system.codedom compiliers section of our standard web config. I investigated the problem a bit. (I also checked the namespace details on msdn to find out abit about it). Amongst many other solutions, I found this post recommending updating the FX_Schema.xml file on our server. (I think this is where the problem is, please correct me if I’m mistaken)

I looked through fx_schema file, and, as defined in the event viewer, the attribute "providerOption" is not in this schema! Here is the copy of the system.codedom section from the FX_schema.xml

<sectionSchema name="system.codedom">
    <element name="compilers">
        <collection addElement="compiler" removeElement="remove" clearElement="clear">
            <attribute name="language" type="string" isCombinedKey="true" />
            <attribute name="extension" type="string" isCombinedKey="true" />
            <attribute name="type" type="string" />
            <attribute name="warningLevel" type="int" />
            <attribute name="compilerOptions" type="string" />
        </collection>
    </element>
</sectionSchema>

I am sure that I can not be the the only person who has this problem, but has anyone else anyone come across this before and found a solution?

EDIT: Another way to produce this quickly is (on IIS 7 in Windows 7)

In IIS Managment console, open your MVC website, in the website home. You should see ASP.NET, IIS, and Managment groups. Under Management, open the "Configuration Editor". I get the error message popping up here!

EDIT: My copy of the web config:

<system.codedom>
    <compilers>
        <compiler language="c#;cs;csharp" extension=".cs" warningLevel="4"
            type="Microsoft.CSharp.CSharpCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
         <providerOption name="CompilerVersion" value="v3.5"/>
         <providerOption name="WarnAsError" value="false"/>
    </compiler>

  <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" warningLevel="4"
            type="Microsoft.VisualBasic.VBCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
    <providerOption name="CompilerVersion" value="v3.5"/>
    <providerOption name="OptionInfer" value="true"/>
    <providerOption name="WarnAsError" value="false"/>
      </compiler>
   </compilers>

</system.codedom>

Answer 1

I’ve managed to recreate the error in IIS by simply going to the system.codedom section of the configuration manager.

I don’t get any error using either a .net3.5 or .net4.0 app but these are very basic test apps, also only .net3.5 test apps put a system.codedom section in the web.config file by default.
.net4.0 simplified the web.config file and moved out a lot of options

I’ve found some information here about possible config conflicts which may be of use

It recomends

The workaround for the second scenario
is to delete or comment out all the
system.web.extensions configuration
section definitions and configuration
section group definitions from the
application-level Web.config file.
These definitions are usually at the
top of the application-level
Web.config file and can be identified
by the configSections element and its
children.

For both scenarios, it is recommended
that you also manually delete the
system.codedom section, although this
is not required

Not exactly the same problem but similar