user32.dll

Implementing Callback Functions
Exemplo EnumWindows

API calls List (USER32.DLL)

The secret life of GetWindowText
“GetWindowText() cannot retrieve text from a window from another application.”

Tutorial: Capturing and Running IE Instances in a Windows control

Working with Win32 API in .NET

Get Current Window Handle and Caption With Windows API In C#

Difference between WM_GETTEXT and GetWindowText?
Question: What is the difference between sending message WM_GETTEXT and calling GetWindowText()?
Answer: You can send WM_GETTEXTLENGTH and WM_GETTEXT message even across processes. GetWindowText takes shortcuts, it tries to directly pass a WM_GETTEXT message to the target windows window function instead of using SendMessage. That does not work across process boundaries.

Enumerating and Restoring Windows Using Callbacks

EnumWindows and EnumChildWindows Callbacks