Problems Detecting Alt Key on the Control.KeyUp event

Question

Hi,

I have a control with KeyDown and KeyUp events as shown below. The problem I am having is that 'x' is TRUE in KeyDown but always FALSE in KeyUp. I am trying to detect the Alt key (as you may have guessed).

Is there a gottcha that I don't know. I mean, when I press Alt it detects it ok but on keyup it's false.

Any suggestions/ideas

Thanks

    private void MyControl_KeyDown(object sender, KeyEventArgs e)
    {
        bool x;
        x = ((int) (e.KeyData & Keys.Alt) != 0);
        x = (e.KeyData & Keys.Alt) == Keys.Alt;
        x = e.Alt;
    }
    private void MyControl_KeyUp(object sender, KeyEventArgs e)
    {
        bool x;
        x = ((int) (e.KeyData & Keys.Alt) != 0);
        x = (e.KeyData & Keys.Alt) == Keys.Alt;
        x = e.Alt;
    }

Answer 1

Are you trying to detect an Alt+[letter] event? Is so, try this:

        private void YourControl_KeyDown(object sender, KeyEventArgs e)
        {
          if((e.Alt) & (e.KeyCode  == Keys.X))
          {
            MessageBox.Show("Alt-X pressed");
          }
        }

---

For just Alt, try this:

    private void YourControl_KeyDown(object sender, KeyEventArgs e)
    { 
        if (e.KeyCode  == Keys.Menu)
        {
            //YourCode
            e.Handled = true;
        }
    }

    private void YourControl_KeyUp(object sender, KeyEventArgs e)
    { 
        if (e.KeyData == Keys.Menu)
        {
            //YourCode
            e.Handled = true;
        }
    }

Answer 2

I hope you're not just setting a bool member variable in your class in response to the Alt key being pressed.

If you want to know if the Alt key is down while executing code in response to other events (eg mouse events) use the Control.ModifierKeys property as it is far more reliable. It also means you don't have a redundant member variable.

If you are actually trying to detect if the user has pressed just a Modifier key by itself then @bluecoder's solution is probably what you want.