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How to PgUp/PgDn with SendKeys to a foreground textbox

I am trying to page up/down the contents of a simple textbox control in a simple Windows Form on NET 6.0, but something is wrong. Textbox shortcuts are enabled (probably why SendKeys.SendWait("^a"); works) and readonly is false.
I have a method (not on the UI thread) that I call to SendKeys.SendWait("{PgUp}"); to the foreground app (which is both the key sender and textbox (with focus) receiver.
If I type PgUp on the keyboard, the textbox pages up as expected.
If I SendKeys.SendWait("^a");, the textbox selects all text as expected.
If I Sendkeys.SendWait("{PgUp}");, the textbox adds a blank line to the bottom of the text.
From this I conclude that my code is working because it sends "^a" and the textbox receives it and selects all text. But somehow the textbox does not handle the "{PgUp}" key, even though it does when the PgUp key is sent by the keyboard.
I've read easily a dozen articles and posts on the web and SO that talk about paging using scrolling events, positioning the caret and then scrolling to the caret, and so on. But none of them say anything about why SendKeys(^a) and keyboard PgUp would work but SendKeys.SendWait("{PgUp}") would fail.
Can anyone tell me what I'm doing wrong and maybe what I need to do (or read) to fix it? Thank you
UPDATE: Jimi asked for some code, so here is the code that I use to send the ^a and the {PgUp} keys. I know this is not on the UI thread because it is executed from a voice-driven recognizer thread. The app is a voice-driven app that displays content in the textbox by textbox.AppendLines calls. I was trying to PgUp and PgDn the multi-line textbox by voice as well.
When I tried to use Send (I normally use .SendWait for everything in other programs), I received the following error message:
System.InvalidOperationException: 'SendKeys cannot run inside this
application because the application is not handling Windows messages.
Either change the application to handle messages, or use the
SendKeys.SendWait method.'
It is true that my app does not intercept Windows messages. I can't figure out why the app can receive and properly process my keyboard keys, and my "^a' shortcut keys, but not the SendWait("{PgUp}") key.
internal static void
HelperPageUp() {
var keys = "{PgUp}";
keys = "^a";
SendKeys.SendWait(keys);
}
I'm starting to think that {PgUp} is never handled by a textbox or control. Instead, probably {PgUp} must be handled by logic in a case statement that converts PgUp "orders" into sets of actions that implement whatever PgUp means to the app that receives the PgUp key. So maybe I will have to add a keystroke handler to the form. Maybe something like this:
textBox1_KeyUp(object sender, KeyEventArgs e) {
// identify the special key and implement what it means
if (e.KeyCode == Keys.PageDown) {
...
e.Handled = true;
}

Yes, my thought at the end of the question was correct. The ^a was handled by the textbox because I had textbox.EnableShortcuts=true;, so the textbox handled the popular ^a shortcut. But keys like {PgUp} are a different matter; they are not included in shortcuts.
The solution was to write code to handle the {PgUp} key explicitly in the form. Here is my code that worked.
void
textBox1_KeyUp(object sender, KeyEventArgs e) {
if (e.KeyCode == Keys.PageUp) {
// page the viewport up; watch for end of content
var charIndex = textBox1.SelectionStart;
var lineIndex = textBox1.GetLineFromCharIndex(charIndex);
// move 20 lines up, but not past zero
var newLine = lineIndex - 20;
var newIndex = Math.Max(0, newLine);
// set the new anchor and scroll to it
var newAnchor = textBox1.GetFirstCharIndexFromLine(newIndex);
textBox1.Select(newAnchor,0);
textBox1.ScrollToCaret();
e.Handled = true;
}

Custom OSK: Listen to TextBox Focus

I have written a custom OnScreen Keyboard as an UserControl to have a better control over what the user can type (Alphanumeric/Numpad/Navigation Keys - stuff like that) and to have a better control over the screen layout at design time.
The OSK works by manipulating the text- and selection-properties/functions of a textbox-control.
My main Problem is how to find the right TextBox to inject text into.
My first, naive approach was to register every TextBox I want to use with the OSK Control manually and use the GotFocus/LostFocus of those registered TextBoxes to determine the active control:
public void RegisterInput(TextBox text) {
if (!_listeners.ContainsKey(text)) {
_listeners.Add(text, modes);
text.GotFocus += Input_OnGotFocus;
text.LostFocus += Input_OnLostFocus;
}
}
private void Input_OnLostFocus(object sender, RoutedEventArgs routedEventArgs) {
if (_focused == sender) {
_focused = null;
IsEnabled = false;
UpdateKeyboardMode(); // << Updates Keyboard layout (Alphanumerical vs Numpad) based on focused control
}
}
private void Input_OnGotFocus(object sender, RoutedEventArgs routedEventArgs) {
_focused = (TextBox) sender;
IsEnabled = true;
UpdateKeyboardMode();
Bindings.Update();
}
I work with Focus here, because I need to determine which kind of keyboard (full-size alphanumerical vs. short numpad) to display for each TextBox. The _focused TextBox is then used to directly inject the pressed keys into it. In the constructor of my Page which also contains the OSK-control I would call RegisterInput() with a reference of each and every TextBox I defined on the page. This works just fine — if I have those references.
But now I am working with UserControls. That also removes the TextBoxes out of reach for direct referencing, but I could write some kind of VisualTree-Scan after InitializeComponent() to find all references and call RegisterInput() on each reference I found. If I only need to do this once, it isn't a problem (altough it is still ugly).
One step further - ListBoxes with dynamicly changing contents and DataTemplates. Now I'd need to rescan the whole VisualTree explicitly everytime something changes. But how to detect those changes?
The question is: Can I get an event as soon as $any element in my VisualTree gets/looses focus, without knowing all those elements beforehand (thus replacing RegisterInput() completely)? Or can I listen to changes to the VisualTree to rescan all controls and then call RegisterInput() manually for every TextBox I found?
The goal is to get a handler called everytime a GetFocus/LostFocus event on any TextBox/Control in the UI is raised so that I can update the keyboard to either display a full-sized alphanumerical keyboard (for default textboxes) or a shortened numpad (e.g. for textboxes bound to numerical backing fields).
Alternatively: Is there any other way to inject text and call UpdateKeyboardMode() to update the keyboard layout as soon as the selected textbox changes?
Other options I thought about include:
Build a custom control which derives from a TextBox and let it register itself to the OSK. I'll probably resort to this method, if I don't find any better way. But this will destroy support for 3rd party libraries in which my control is not present and thus does not use the "special magical textbox with osk support".
Don't use events at all. Get the currently focused TextBox with the FocusManager as soon as the user presses a key on my OSK and inject text into the focused instance. Problem with this approach is, that it completely destroys the capability to adapt the OSK to different input types (alphanumerical vs only Numpad), because I cannot determine the keyboard type I need before pressing a key.
Rescan the VisualTree with a timer. Won't do that, thats simply too much of a hack.
Use the OnScreen-Keyboard supplied by Win10 IoT. Two problems: It has no designtime support and is displayed above elements, even if the focused element is directly underneath the keyboard (acceptable if neccessary), but I don't know of a way to change the keyboard "layout" between a full-sized alphanumeric keyboard and a shortened Numpad which only contains numbers and some keys. Also it does not allow to use custom keys (e.g. arrow keys for navigation, custom return key handling).

After a discussion in the chat forum, the actual problem isn't to create a Custom OSK control and use that to interact with the TextBoxs but instead, it's "being bound to use custom control" wrapping a textbox everywhere a OSK needs to be shown.
The Solution would be to listen to the OS-OSK events and when they are triggered, pop up the Custom OSK this ways you won't have to wrap a Textbox in a user control and use that throughout your project.
Link to the Documentation: - respond to the presence of the touch keyboard

Trying to Select the value of a DropDown in a WebBrowser Control (AJAX)

I'm trying to select a value from a second dropdown list which is updated dynamically.
Here is my code for the second dropdown:
HtmlElementCollection select = x.GetElementsByTagName("select");
foreach (HtmlElement el in select)
{
if (el.Name == "color")
{
foreach (HtmlElement ele in el.GetElementsByTagName("option"))
{
//MessageBox.Show(ele.InnerHtml);
if (ele.InnerText == "green")
{
ele.Focus();
ele.SetAttribute("selected", "selected");
el.InvokeMember("onchange");
ele.RemoveFocus();
break;
}
}
}
}
The code works but only if I use the MessageBox statement.
If I comment the MessageBox line, the dropdown option won't be selected.
What event is the MessageBox raising ?

I don't have an explanation for the behavior that you are seeing but in my extensive work with WebBrowser controls in the past I have come across some unexplicable behaviors, too.
Anyway, here are a few things you can try:
I assume that you verified by other means that when you don't have a MessageBox statement placed, that the inner part of the if clause gets executed?
Just assign the ele.InnerHtml to a string (maybe do something with the string to guarantee that JITing doesn't optimize it away. Accessing InnerHtml might trigger something within the element that causes the event to work.
Instead of setting the "selected" attribute and invoking "onchange", try setting ele.selectedIndex of IHTMLSelectElement.
Generally, you should not have to invoke "onchange" explicitly. If JavaScript code has subscribed to that event, IE should automatically call that.
Is this method being executed on the UI thread? I found that WebBrowser can act weird when you access the DOM from a background thread. If not the UI thread, use Invoke to marshal method execution to the UI thread.

Binding between controls in Windows Forms

Is there a way to make a control dependent on another control? I have a combo box and a button, and I need the button to be enabled if and only if there is an item selected in the combo box.
I know I can set the Enabled property of the button inside the SelectedIndexChanged callback, but then it will require some code, and besides there's an issue with what initial state the button would have. So I'm looking for something that wouldn't require manually handing events, is this possible?
Thanks!

No, there is no way in winforms to do this without code. What I usually do is to collect all such state-setting code into one specific method:
private void SetControlStates()
{
theButton.Enabled = theComboBox.SelectedIndex >= 0;
// code for other controls follow here
}
Then I trigger this method from all over the place, as soon as there is an interaction that may lead to the state changing (including the last thing I do when the form has finished loading; that takes care of initial state). If you want to avoid unnecessary assignments, just add code to check the value first:
private void SetControlStates()
{
bool buttonEnabled = theComboBox.SelectedIndex >= 0;
if (theButton.Enabled != buttonEnabled) theButton.Enabled = buttonEnabled;
// code for other controls follow here
}

Bring Winforms control to front

Are there any other methods of bringing a control to the front other than control.BringToFront()?
I have series of labels on a user control and when I try to bring one of them to front it is not working. I have even looped through all the controls and sent them all the back except for the one I am interested in and it doesn't change a thing.
Here is the method where a label is added to the user control
private void AddUserLabel()
{
var field = new UserLabel();
userContainer.Controls.Add(field);
SendLabelsToBack(); // Send All labels to back
userContainer.Controls[field.FieldName].BringToFront();
}
Here is the method that sends all of them to the back.
private void SendLabelsToBack()
{
foreach (var label in userContainer.Controls);
label.SendToBack();
}

Yeah, there's another way. The Controls.SetChildIndex() also changes Z-order. The one with index 0 is the one on top. Doesn't buy you anything though, BringToFront() uses this method.
Your SendLabelsToBack() method as given cannot work, it will also send the label to added to the back. But your next statement fixes that again.
Okay, that doesn't work, which means the BringToFront() method doesn't get executed. Look in the Output window for a "first chance exception" notification. As written, your SendLabelsToBack() will cause an exception if the user control contains any control other than a UserLabel. Also, set a breakpoint after the BringToFront() call and check the value of userContainer.Controls[0].Name when it breaks.

Controls' z-index is per-container.
If you call BringToFront on a control that is inside a container (such as a Panel), it will not bring the container to the front.
Therefore, the control will only go in front of other controls in that container.
To see what containers your controls are in, you can use the Document Outline pane in the View menu.
EDIT: Your userContainer control is probably behind a different control.

Have you tried Invalidate() after BringToFront()? BringToFront does not raise the Paint event
try this:
private void SendLabelsToBack()
{
foreach (var label in userContainer.Controls)
{
label.SendToBack();
label.Invalidate();
}
}

I think you just need to change your last line:
userContainer.Controls[field.FieldName].BringToFront();
to this:
userContainer.Controls[field.Name].BringToFront();
When you use a string as the indexer for the Controls collection, it goes by the Name property of the control (not the FieldName property).
Since you're just trying to bring the most recently-added control to the top, this would also work:
userContainer.Controls[userContainer.Controls.Count - 1].BringToFront();

From my experience looks like windows puts all controls belonging to one graphic container(pane, group box...etc) in a software collection. The collection is ordered by child index which is a property of every control in that container.
The trick is that children with the same index can and do exists. In this case windows will paint those children ordered relative to others but between them it will paint them in the reverse order they had been added to the container.
Long story short: for one container-you need to make sure controls have different indexes by changing ALL NOT just SOME of the indexes when you want to change the z-order. For example:
foreach (Control newControl in TopControl.Controls)
{
TopControl.Controls.SetChildIndex(newControl,indexlogic(newControl));
}
where indexLogic(newControl ) is your method of calculation of the index of particular control.