如何在csv文件的下一个开头的下一行写？

Question

在第一次运行时,我的程序在第一行写入csv文件,但是,当我在第二行运行我的程序时...第三行...它运行在第一行...我怎么能纠正它？

我想输入所有进入我程序的CSV文件.

代码如下:

private void WriteToCsvFile()
{
    var us = users.ElementAt(0);
    string names = "Number',";
    string userAnswer = (us.userName + ",");
    foreach (string ss in user)
    {
        string str = Path.GetFileName(ss);
        names = names + str + ",";
    }
    foreach (string ans in us.answer)
    {
        userAnswer = userAnswer + ans + ",";
    }

    using (StreamWriter sw = new StreamWriter("EntranceLog.csv"))
    {
        sw.WriteLine(names);
        sw.WriteLine(userAnswer);

    }

    this.Close();
}