Feature detection when P/Invoking in C# and .NET

i'm trying to find a good way to detect if a feature exists before P/Invoking. For example calling the native StrCmpLogicalW function:

[SuppressUnmanagedCodeSecurity]
internal static class SafeNativeMethods
{
   [DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
   public static extern int StrCmpLogicalW(string psz1, string psz2);
}

will crash on some systems that do not have this feature.

i don't want to perform version checking, as that is bad practice, and can sometimes just be wrong (for example when functionality is back-ported, or when the functionality can be uninstalled).

The correct way, is to check for the presence of the export from shlwapi.dll:

private static _StrCmpLogicalW: function(String psz1, String psz2): Integer;
private Boolean _StrCmpLogicalWInitialized;

public int StrCmpLogicalW(String psz1, psz2)
{
    if (!_StrCmpLogialInitialized)
    {
        _StrCmpLogicalW = GetProcedure("shlwapi.dll", "StrCmpLogicalW");
        _StrCmpLogicalWInitialized = true;
    }

    if (_StrCmpLogicalW)
       return _StrCmpLogicalW(psz1, psz2)
    else
       return String.Compare(psz1, psz2, StringComparison.CurrentCultureIgnoreCase);
}

The problem, of course, is that C# doesn't support function pointers, i.e.:

_StrCmpLogicalW = GetProcedure("shlwapi.dll", "StrCmpLogicalW");

cannot be done.

So i'm trying to find alternative syntax to perform the same logic in .NET. i have the following pseudo-code so far, but i'm getting stymied:

[SuppressUnmanagedCodeSecurity]
internal static class SafeNativeMethods
{
   private Boolean IsSupported = false;
   private Boolean IsIniti