C#读取中文字符及清空缓冲区

有一个txt的中英文语料库文件，内容是英文一句中文一句相间的，共3000行，需要把英文句和中文句分开，放在单独的txt文件中。开时始，得到的中文文件中的字符是乱码的，鸟符号看的头晕。于是就细究streamreader读取的编码格式，默认的编码是ascii，单字节的，就尝试utf8，乱码；尝试gb2312，OK！

可另一个问题又出现了，得到的两个文件的行数都不到1500行，尝试N次还是不行，很郁闷。google了下，看到try catch，就想到释放缓冲区，结果很HAPPY！

private static void FnFileProcess()
        {
            StreamReader reader = new StreamReader(@"d:\1500.txt", Encoding.GetEncoding("GB2312"));
            StreamWriter writerEn = new StreamWriter(@"d:\English.txt", false, Encoding.UTF8, 1024);
            StreamWriter writerCh = new StreamWriter(@"d:\Chinese.txt", false, Encoding.UTF8, 1024);
            try
            {
                int i = 1;
                for (String line = reader.ReadLine(); line != null; line = reader.ReadLine())
                {
                    if (i % 2 == 1)
                    {
                        writerEn.WriteLine(line);
                    }
                    else
                    {
                        writerCh.WriteLine(line);
                    }
                    i++;
                }
                Console.WriteLine(i + "\tOK");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            finally
            {
                //不清空缓冲区，得到的文件总是少几十行
                writerEn.Flush();
                writerCh.Flush();
            }
        }