我是新手，问个关于创建文件夹的问题...d

Question

DirectoryInfo di = new DirectoryInfo("E://"+username.Text);
            if (di.Exists == false)
                di.Create();
            DirectoryInfo dis = di.CreateSubdirectory("data");
这里创建文件的只是绝对路径，但是我不想用绝对路径，想用相对路径，想请问一下，应该怎么写？把文件创建在该软件的根目录下。

Answer 1

DirectoryInfo di = new DirectoryInfo(Application.StartupPath+"\\"+username.Text);
            if (di.Exists == false)
                di.Create();
            DirectoryInfo dis = di.CreateSubdirectory("data");
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Answer 2

string FolderPath = Server.MapPath("/LoginLog/" + System.DateTime.Now.ToString("yyyy-MM"));
            if (!Directory.Exists(FolderPath))
            {
                //文件夹不存在则创建
                Directory.CreateDirectory(FolderPath);
                //写入日志
                string FilePath = Server.MapPath("/LoginLog/" + DateTime.Now.ToString("yyyy-MM") + "/" + DateTime.Now.ToString("yyyy-MM-dd"));
                if (!Directory.Exists(FilePath))
                {
                    //如果文件存在则写入日志
                    using (StreamWriter writer = File.AppendText(FilePath + ".txt"))
                    {
                        writer.WriteLine("[登录成功！][用户IP]：" + ip + "； [登录时间]：" + DateTime.Now);
                        writer.Flush();
                        writer.Close();
                    }
                }
                else
                {
                    //如果文件不存在当前目录下创建一个文本文件  
                    StreamWriter writer = new StreamWriter(FilePath + ".txt");                    writer.WriteLine("[登录成功！][用户IP]：" + ip + "； [登录时间]：" + DateTime.Now);
                    writer.Flush();
                    writer.Close();
                }
            }
            else
            {
                //文件夹存在则写入日志
                string FilePath = Server.MapPath("/LoginLog/" + DateTime.Now.ToString("yyyy-MM") + "/" + DateTime.Now.ToString("yyyy-MM-dd"));
                if (!Directory.Exists(FilePath))
                {
                    //如果文件存在则写入日志
                    using (StreamWriter writer = File.AppendText(FilePath + ".txt"))
                    {
                        writer.WriteLine("[登录成功！][用户IP]：" + ip + "； [登录时间]：" + DateTime.Now);
                        writer.Flush();
                        writer.Close();
                    }
                }
                else
                {
                    //如果文件不存在当前目录下创建一个文本文件  
                    StreamWriter writer = new StreamWriter(FilePath + ".txt");                    writer.WriteLine("[登录成功！][用户IP]：" + ip + "； [登录时间]：" + DateTime.Now);
                    writer.Flush();
                    writer.Close();
                }
            }
            Response.Redirect("ManageLogin/");