How to use Windows On-Screen Keyboard in C# WinForms

Question 1

I am now launching the "Touch Keyboard" as opposed to the "On-Screen Keyboard" (which is the keyboard I wanted on Windows 8 anyway) with:

string progFiles = @"C:\Program Files\Common Files\Microsoft Shared\ink";
string keyboardPath = Path.Combine(progFiles, "TabTip.exe");

this.keyboardProc = Process.Start(keyboardPath);

This works on my Win7 and Win8, regardless of my 32-bit app on 64-bit OS. However, I still have the problem of programmatically closing the keyboard when I'm done. The process, this.keyboardProc, does not seem to get the handle, and immediately has property HasExited = true. This means my attempts to close or kill it fail.

According to this thread, if the user manually opens the keyboard (or I programmatically launch it), the keyboard will not automatically close/hide when the text field loses focus: Windows 8 - How to Dismiss Touch Keyboard? I tried the workaround of setting the focus to a hidden button, but since I launched the keyboard myself, it doesn't close automatically.

Question 2

I had trouble closing the on screen keyboard. You can start the Touch Keyboard with

string progFiles = @"C:\Program Files\Common Files\Microsoft Shared\ink";
string onScreenKeyboardPath = System.IO.Path.Combine(progFiles, "TabTip.exe");
onScreenKeyboardProc = System.Diagnostics.Process.Start(onScreenKeyboardPath);

and close all keyboards with

//Kill all on screen keyboards
Process[] oskProcessArray = Process.GetProcessesByName("TabTip");
foreach (Process onscreenProcess in oskProcessArray)
{
    onscreenProcess.Kill();
}

For some reason onScreenKeyboardProc.Kill() or .Close() doesn't work.

Question 3

For the keyboard to open up automatically, the controls have to implement some UI Automation control patterns, specifically ITextProvider/IValueProvider. It is a nuisance, but it works (and it is a cleaner way than launching some *.exe)

I wrote a sample app and a short article here: http://blog.tombam.net/implementing-textbox-with-on-screen-touch-keyboard-part-1/

Question 4

The touch keyboard leverages the UI automation. For some reasons that are a mystery to me, the standard Windows edit box does not implement UI automation, while other controls, like combo box, do.

One can use implementation of UI automation from UIAutomationClient.dll.

For the UI automation to be magically injected into an application, class initializer of the assembly internal class UiaCoreApi have to be triggered.

On can achieve that for example by calling seeming no-op:

AutomationElement.FromHandle(IntPtr)(-1)

Another way is to implement automation UI explicitly. For that implement the ITextProvider/IValueProvider interfaces for the respective input control.

To bind the implementation of the interfaces to the control, handle WM_GETOBJECT window message with lParam = RootObjectId.

For an example of implementation, see

tombam's answer to this question;
or directly poster's article Implementing TextBox with on-screen touch keyboard.

Though interestingly, controls, for which touch keyboard works out-of-the-box (like combo box or password edit box, see the answer), do not implement the WM_GETOBJECT/RootObjectId. There must be a different machinery behind them.

The most common "solution" to this problem, to explicitly popup the keyboard by running the TabTip.exe or osk.exe, is hardly acceptable.

If for nothing else, then because there's no clean way to hide the keyboard opened by running the TabTip.exe (solutions include hacks like killing the process or sending Esc key).

And actually the above hack does not seem to work anymore in Windows 10 Anniversary Update: Show touch keyboard (TabTip.exe) in Windows 10 Anniversary edition.

Question 5

Starting TabTip.exe no longer works in Widnows 10 Anniversary Edition. I discovered an undocumented COM interface for controlling the touch keyboard. Check the code here https://stackoverflow.com/a/40921638/332528

Question 6

I've surfing here and somewhere else then I implement this:

using System.Diagnostics; // remember use this

public partial class Window1 : Window
{

    public Process _p = null;
   
    public Window1()
    {
        InitializeComponent();          
    }

    public void Button_Click(object sender, RoutedEventArgs e)
    {
        if (_p != null)
        {
            _p.Kill();
            _p.Dispose();
            _p = null;
        }
        _p = Process.Start(@"C:\Program Files\Common Files\microsoft shared\ink\TabTip.exe");    
    }

    private void Acceso_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        if (_p != null)
        {
            _p.Kill();
            _p.Dispose();
            _p = null;
        }
    }
}

It works properly, so I share it here in case it helps as your info helped me.