将xml从文本框写入现有的xml文件而不替换旧文本，只需添加新文本

So... I have 2 textboxes and 1 button. And when I input data to those textboxes, and click the button, I would like it to enter xml file and add new element with attributes to it, without replacing it. After a lot of browsing I managed to do something that replaced all text in my xml file, or I got an error, so I decided to post a question here.So... I have 2 textboxes and 1 button. And when