读取n个文本文件，把文件内容合并到一个文本文件中。主要用了FileStream的ReadByte和WriteByte方法：

class FileCombine
{
     public void CombineFile(String[] infileName,String outfileName)
     {     
            int b;
            int n=infileName.Length;
            FileStream[] fileIn=new FileStream[n];
            using (FileStream fileOut = new FileStream(outfileName, FileMode.Create))
            {
                for (int i = 0; i < n; i++)
                {
                    try
                    {
                        fileIn[i] = new FileStream(infileName[i], FileMode.Open);
                        while ((b = fileIn[i].ReadByte()) != -1)
                            fileOut.WriteByte((byte)b);
                    }
                    catch (System.Exception ex)
                    {
                        Console.WriteLine(ex.Message);
                    }
                    finally
                    {
                        fileIn[i].Close();
                    }
                   
                }
            }
     }
}

调用方法如下：

class TestCombine
{
     public static void Main(String[] args)
     {
         FileCombine c=new FileCombine();
         String[] file=new String[2];
         file[0]="aa.txt";
         file[1]="bb.txt";
         c.CombineFile(file,"cc.txt");
    }
}