How to control a winforms application using another?

Question

I have a winforms Application 1 which looks like this:

This application is already built so I can't change its source code.

I want to write another winforms application, which can run hidden and auto fill that textbox in Application 1 then click the button.

But I don't know where to start. I Hope you can help me with some keyword, or technique that I can use in this situation. Thank you.

Answer 1

我找到了一个很好的示例，可以解决我的问题并轻松理解http://www.codeproject.com/Articles/33049/WPF-UI-Automation