Compiling with CodeDomProvider doesn't allow new features of C# or VB

var csc = new CSharpCodeProvider(new Dictionary<string, string>() { { "CompilerVersion", "v3.5" } });

<system.codedom>
  <compilers>
    <compiler
      language="vb;vbs;visualbasic;vbscript"
      extension=".vb"
      type="Microsoft.VisualBasic.VBCodeProvider, System,
        Version=2.0.3600.0, Culture=neutral,
        PublicKeyToken=b77a5c561934e089"
      compilerOptions="/optimize"
      warningLevel="1" >
      <providerOption
        name="CompilerVersion"
        value="v3.5" />
    </compiler>
    <compiler
      language="c#;cs;csharp"
      extension=".cs"
      type="Microsoft.CSharp.CSharpCodeProvider, System,
        Version=2.0.3600.0, Culture=neutral,
        PublicKeyToken=b77a5c561934e089"
      compilerOptions="/optimize"
      warningLevel="1" >
      <providerOption
        name="CompilerVersion"
        value="v3.5" />
    </compiler>
  </compilers>
</system.codedom>