OpenFileDialog FolderBrowserDialog

  OpenFileDialog ofd = new OpenFileDialog();
            ofd.Title = "打开(Open)";
            ofd.FileName = "";
            ofd.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

//为了获取特定的系统文件夹，可以使用 

//System.Environment类的静态方法GetFolderPath()。

//该方法接受一个Environment.SpecialFolder枚举，其中可以定义要返回路径的哪个系统目录

            ofd.Filter = "文本文件(*.txt)|*.txt";
            ofd.ValidateNames = true;     //文件有效性验证ValidateNames，验证用户输入是否是一个有效的Windows文件名
            ofd.CheckFileExists = true;  //验证路径有效性
            ofd.CheckPathExists = true; //验证文件有效性
            try
            {
                if (ofd.ShowDialog() == DialogResult.OK)
                {
                    //StreamReader sr = new StreamReader(ofd.FileName, System.Text.Encoding.Default);
                    //this.richTextBox1.Text = sr.ReadToEnd();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }

--------------------------------

            FolderBrowserDialog folderBrowserDialog1 = new FolderBrowserDialog();

            folderBrowserDialog1.SelectedPath = textBox1.Text;

            if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)

            {

                textBox1.Text=folderBrowserDialog1.SelectedPath;

            }