using System;
using System.IO;
using System.Text;
using System.Runtime.InteropServices;

//big5繁体转换简体的程序
public class EncodeTool
{
 
 [DllImport("kernel32.dll", EntryPoint = "LCMapStringA")]
    public static extern int LCMapString(int Locale, int dwMapFlags, byte lpSrcStr, int cchSrc, byte lpDestStr, int cchDest);
   
 const int LCMAP_SIMPLIFIED_CHINESE = 0x02000000;
 const int LCMAP_TRADITIONAL_CHINESE = 0x04000000;

    public static void Main (String args)
    {
  if (args.Length<1)
  {
   Console.WriteLine("请指定路径！");
  }
  String files=Directory.GetFiles(args[0]);
  if(args.Length==2)
   files=Directory.GetFiles(args[0],args);
  String dir=args[0]+"\\conv";
  if(!Directory.Exists(dir)){
   Directory.CreateDirectory(dir);
  }
  for(int i=0;i   StreamReader sr = new StreamReader(files[i],Encoding.GetEncoding("big5"));
   String lines=sr.ReadToEnd();
   sr.Close();
   lines=ConvertString(lines);
   //Console.WriteLine(lines);
   StreamWriter sw = new StreamWriter(dir+"\\"+files[i],false,Encoding.GetEncoding("gb2312"));
   sw.WriteLine(lines);
   sw.Close();
   Console.WriteLine("转换 {0} ok!",files[i]);
  }
 }

 public static String ConvertString(String lines){
  Encoding gb2312 = Encoding.GetEncoding(936);
  byte src=gb2312.GetBytes(lines);
  byte dest = new byte[src.Length];
  LCMapString(0x0804, LCMAP_SIMPLIFIED_CHINESE, src, -1, dest, src.Length);
  return gb2312.GetString(dest);
 }
}

作者 未知 来源http://www.cnblogs.com/midea0978/archive/2006/05/25/408582.html