P/Invoke and wrapper method for RoResolveNamespace

ResolveNamespace.cs

using System;
using System.Linq;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.WindowsRuntime;



class WinRTInterop
{
    public class ResolvedNamespaces
    {
        public string[] MetadataFilePaths;
        public string[] SubNamespaces;
    }

    public static ResolvedNamespaces ResolveNamespace(string namespaceName, string windowsMetadataDir = null, string[] packageGraphDirs = null)
    {
        UInt32 tempPathsCount, tempNamespacesCount;
        IntPtr[] tempPaths = null;
        IntPtr[] tempNamespaces = null;
        IntPtr[] tempPackageGraphDirs = null;

        try
        {
            if (packageGraphDirs != null)
            {
                tempPackageGraphDirs = packageGraphDirs.Select(dir => WindowsRuntimeMarshal.StringToHString(dir)).ToArray();
            }

            var hr = RoResolveNamespace(
                namespaceName,
                String.IsNullOrEmpty(windowsMetadataDir) ? string.Empty : windowsMetadataDir,
                tempPackageGraphDirs == null ? 0 : (uint)tempPackageGraphDirs.Length,
                tempPackageGraphDirs,
                out tempPathsCount, out tempPaths, out tempNamespacesCount, out tempNamespaces);

            var metadataFilePaths = tempPathsCount == 0 ? new string[0] : tempPaths.Select(p => WindowsRuntimeMarshal.PtrToStringHString(p)).ToArray();
            var subNamespaces = tempNamespacesCount == 0 ? new string[0] : tempNamespaces.Select(ns => WindowsRuntimeMarshal.PtrToStringHString(ns)).ToArray();

            return new ResolvedNamespaces
            {
                MetadataFilePaths = metadataFilePaths,
                SubNamespaces = subNamespaces,
            };
        }
        finally
        {
            Action<IntPtr[]> FreeHStrings = ipar =>
            {
                if (ipar != null)
                {
                    foreach (var hstr in ipar) { WindowsRuntimeMarshal.FreeHString(hstr); }
                }
            };

            FreeHStrings(tempNamespaces);
            FreeHStrings(tempPackageGraphDirs);
            FreeHStrings(tempPaths);
        }
    }

    [DllImport("WinTypes.dll")]
    static extern UInt32 RoResolveNamespace(
        [MarshalAs(UnmanagedType.HString)] string name,
        [MarshalAs(UnmanagedType.HString)] string windowsMetaDataDir,
        UInt32 packageGraphDirsCount,
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] IntPtr[] packageGraphDirs,
        out UInt32 metaDataFilePathsCount,
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 4)] out IntPtr[] metaDataFilePaths,
        out UInt32 subNamespacesCount,
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 6)] out IntPtr[] subNamespaces);

}