Consider the following code:
Window myWindow = new MyWindowSubclass();
myWindow.BringIntoView();
myWindow.Show();
// Code which is effective as pressing the maximize button
Also, how to detect if the window is indeed in maximized state.
In WPF, you can use the WindowState property:
myWindow.WindowState = WindowState.Maximized;
You can of course query that property to obtain the current window state:
if (myWindow.WindowState == WindowState.Maximized) {
// Window is currently maximized.
}