Question

In WPF when you make a label like this:

<Label Content="_My Label"/>

Then when you run the app and press the Alt key it will show the “M” underlined.

We have our own custom hotkey Attached Property that allows us to use Ctrl as well as Alt.

Problem is that only Alt will show the underscores.

Is there a way to show the underscore when the Ctrl key is pressed?

NOTE: I do NOT want to send a programmatic Alt KeyPress in the background when Ctrl is pressed. That will just confuse my shortcut system.

Answer 1

Ok! I have got a solution to show the _ for hot-keys without Alt pressed but Ctrl pressed.

Here is how to Do it :

---

Small Code to Press a KeyBoard Key dynamically :

//<summary>
//Function to Perform a Keyboard KeyPress.
//</summary>
void PressKey(Key KeyboardKey)
{
    KeyEventArgs args = new KeyEventArgs(Keyboard.PrimaryDevice,
    Keyboard.PrimaryDevice.ActiveSource, 0, Key.LeftAlt);
    args.RoutedEvent = Keyboard.KeyDownEvent;
    InputManager.Current.ProcessInput(args);
}

---

Code to Append and Remove HotKeyChar :

//<summary>
//Function to Append a HotKeyChar to a Content of a Control.
//</summary>
void AppendHotKeyChar(ContentControl Ctrl, int KeyIndex)
{
    if (Ctrl.Content.ToString().Substring(KeyIndex, 1) != "_")
    {
        Ctrl.Content = "_" + Ctrl.Content;
    }
}
//<summary>
//Function to Remove a HotKeyChar to a Content of a Control.
//</summary>
void RemoveHotKeyChar(ContentControl Ctrl, int KeyIndex)
{
    if (Ctrl.Content.ToString().Substring(KeyIndex, 1) == "_")
    {
        Ctrl.Content = Ctrl.Content.ToString().Remove(KeyIndex, 1);
    }
}

---

XAML Code for Button Bt1 :

<Button x:Name="Bt1" Content="Button" HorizontalAlignment="Left" Margin="169,97,0,0" VerticalAlignment="Top" Width="75"/>

---

Code for Window.Loaded event of the MainWindow (e.g. MainWindow1_Loaded) :

PressKey(Key.LeftAlt);

---

Code for Window.KeyDown event of the MainWindow (e.g. MainWindow1_KeyDown) :

if (e.Key == Key.LeftCtrl)
{
    AppendHotKey(Bt1, 0);
}

---

Code for Window.KeyUp event of the MainWindow (e.g. MainWindow1_KeyUp) :

if (e.Key == Key.LeftCtrl)
{
    RemoveHotKey(Bt1, 0);
}

---

Now, When you start your app the Alt will be pressed once dynamically.

And now every-time you press Ctrl, your Control.Content will be Appended with a _ and so the HotKey will appear underlined!
But one remark is that you should create Control.Content without HotKeyChar '_' but keep an Index of where your _ will be appended.

But keep in mind that if Alt is pressed again in your app, The code will not work anymore. So, you have to press the Alt again to make the code work!

Best way to appending and removing a HotKeyChar :

• Create an instance of List<KeyValuePair<int, Control>> to store the Index of the HotKeyChar and the Control.
• And now in the KeyDown event just loop through the KeyValuePair<...> in the List<...>..appending the _.
• In the KeyUp event again just loop through the KeyValuePair<...> in the List<...>..removing the _.

Hope it Helped!