Greg Young

static bool IsClrImage( string fileName ) {

      FileStream fs = null;

      try {

            fs = new FileStream( fileName, FileMode.Open, FileAccess.Read,

                  FileShare.Read );

            byte[] dat = new byte[300];

            fs.Read( dat, 0, 128 );

            if( (dat[0] != 0x4d) || (dat[1] != 0x5a) ) // "MZ" DOS header

                  return false;

            int lfanew = BitConverter.ToInt32( dat, 0x3c );

            fs.Seek( lfanew, SeekOrigin.Begin );

            fs.Read( dat, 0, 24 ); // read signature & PE file header

            if( (dat[0] != 0x50) || (dat[1] != 0x45) ) // "PE" signature

                  return false;

            fs.Read( dat, 0, 96 + 128 ); // read PE optional header

            if( (dat[0] != 0x0b) || (dat[1] != 0x01) ) // magic

                  return false;

            int clihd = BitConverter.ToInt32( dat, 208 ); // get IMAGE_COR20_HEADER

            rva-address

                  return clihd != 0;

      }

      catch( Exception ) {

            return false;

      }

      finally {

            if( fs != null )

                  fs.Close();

      }

}