Get Language Id for File (Part 1)

RealVersionInfo.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Permissions;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;

namespace VersionInfo
{
    public class RealVersionInfo
    {
        public string FileName { get; set; }

        public int LanguageId { get; set; }

        private RealVersionInfo(string filename)
        {
            FileName = filename;
        }

        public unsafe static RealVersionInfo GetVersionInformation(string filename)
        {
            if(!File.Exists(filename))
            {
                // Check for read access - exists errors if can't be read, but below will only throw an error when access fails, but file exists
                new FileIOPermission(FileIOPermissionAccess.Read, Path.GetFullPath(filename)).Demand();
                throw new FileNotFoundException(filename);
            }

            int handle;
            int infoSize = NativeMethods.GetFileVersionInfoSize(filename, out handle);
            RealVersionInfo rvi = new RealVersionInfo(filename);

            if(infoSize != 0)
            {
                byte[] mem = new byte[infoSize];
                fixed(byte* memPtr = mem)
                {
                    IntPtr memIntPtr = new IntPtr((void*)memPtr);

                    bool success = NativeMethods.GetFileVersionInfo(filename, 0, infoSize, new HandleRef(null, memIntPtr));

                    if (success)
                    {
                        rvi.LanguageId = GetVarEntry(memIntPtr);
                    }
                }
            }

            return rvi;
        }

        private static int GetVarEntry(IntPtr memPtr)
        {
            IntPtr memRef = IntPtr.Zero;
            int memLen;

            if (NativeMethods.VerQueryValue(new HandleRef(null, memPtr), "\\VarFileInfo\\Translation", ref memRef, out memLen))
            {
                return (Marshal.ReadInt16(memRef) << 16) + Marshal.ReadInt16((IntPtr)((long)memRef + 2));
            }

            return 0x040904E4;
        }
    }
}