Why is my WPF textbox “kinda” readonly?

I was encountering a problem very similar to this. After doing a little research, I found a similar problem listed in MSDN:

http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/c68d5f3c-c8cc-427d-82e3-6135d075a304/

According to the answer to the post, the problem has to do with WPF and WinForms having two very different ways of handling text input. Fortunately, the post listed above gives the following solution:

When launching the window, use ElementHost.EnableModelessKeyboardInterop(window1). Note that this is a static method – you do not have to instantiate the ElementHost class.

For example,

Window window1 = new Window();
ElementHost.EnableModelessKeyboardInterop(window1);
window1.Show();

This solved the problem for me. Hope this helps.