Getting Text from any External Window in C#

To get the text of an external window you could use the GetForegroundWindow and the GetWindowTextAPI functions. Here is a small example of its usage:

public partial class Form1 : Form
    {
        [DllImport("user32.dll")]

        static extern int GetForegroundWindow();

        [DllImport("user32.dll")]

        static extern int GetWindowText(int hWnd, StringBuilder text, int count); 
        //Use SetWindowPos to make app alwaysontop

        public Form1()
        {
            InitializeComponent();
        }

        private void GetActiveWindow()
        {

            const int nChars = 256;
            int handle = 0;
            StringBuilder Buff = new StringBuilder(nChars);

            handle = GetForegroundWindow();

            if (GetWindowText(handle, Buff, nChars)  0)
            {
                this.captionWindowLabel.Text = Buff.ToString();
                this.IDWindowLabel.Text = handle.ToString();
            }

        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            GetActiveWindow();

        }

    }