C# 从字符串中分离文件路径、文件名及扩展名的操作

private void btn_select_file_Click(object sender, EventArgs e)
{
    OpenFileDialog openFileDialog = new OpenFileDialog();
    if (openFileDialog.ShowDialog() == DialogResult.OK)
    {
        //string filePathALL = openFileDialog.FileName;
        string filePathALL = "C:\\decktop\\file\\books\\C#学习.exe";
        //文件路径
        string str_path = filePathALL.Substring(0, filePathALL.LastIndexOf("\\") + 1);
        //文件名字
        string str_name = filePathALL.Substring(filePathALL.LastIndexOf("\\") + 1,
                    filePathALL.LastIndexOf(".") - (filePathALL.LastIndexOf("\\") + 1));
        //文件扩展名
        string str_exc = filePathALL.Substring(filePathALL.LastIndexOf(".") + 1,
                    filePathALL.Length - filePathALL.LastIndexOf(".") - 1);
        //string str_exc = filePathALL.Split('.')[1].ToString();   // 也可以使用Split方法
        lbl_file_path.Text = "文件路径：" + str_path;
        lbl_file_name.Text = "文件名称：" + str_name;
        lbl_file_exc.Text = "文件扩展时：" + str_exc;
    }
}