文件操作，Io流。

 private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            String path = @"F:\666.text";
            //创建文件流.
            Stream fs = new FileStream(path, FileMode.Open);
            //创建写入器.
            StreamReader sr = new StreamReader(fs, Encoding.Default);
            //将录入的内容写入文件.
            string src = sr.ReadToEnd();
            //关闭写入器
            sr.Close();
            //关闭文件流.
            fs.Close();
            textBox1.Text = src;
        }
    }

//创建文件流.
FileStream myfs=new FileSteam(path,FileMode.Open);
//创建读取器.
StreamReader mySr=new StremReader(myfs,Encoding.Default);
//读取文件所有内容
content = mySr.ReadToEnd();
txtContent.Text=Content;
//关闭读取器.
mySc.Close();
//关闭文件流.
myfs.Close();

读取目录下的子目录信息。
private void BindInfo(TreeNode node)
{
DirectoryInfo directoryInfo =new DirectoryInfo(node.Tag.ToString());
DirectoryInfo[] dirs = directoryInfo.GetDirectories();
foreach(DirectoryInfo di in dirs)
{
TreeNode temp =new TreeNode();
temp.Text=di.Name;
temp.Tag=di.FullName;
node.nodes.Add(temp);
    }
}