Cannot capture KeyDown event for UP/DOWN-Arrow-Keys in Windows Form

Question

In C# Winforms I try to capture the KeyDown event for the Up-arrow and down-arrow keys. Therefore I did the following:

set the KeyPreview property of the form to true
override of the forms 'OnKeyDown' method

Anyway, the method is never called for the up-/ down-keys, although it is called for the left-/ right-arrow-keys for example. Then I tried to override the forms 'OnKeyUp' method too, just for testing. The strange thing is now that the 'OnKeyUp' method is called for the up-/ down-arrows too. I also tried to override 'ProcessCmdKey', with the same result: it is not called for the up-/ down-arrows.

The thing why I can't use the KeyUp event is that I need to realize if the keys keep pressed for a time so I need the event to get called multiple times which isn't the case for KeyUp.

Any suggestions on what could be the problem here?

Jack Jack · Accepted Answer · 2013-06-18T09:03:20

private bool downKey = false, rightKey = false, leftKey = false;

private void TetrisGame_KeyDown(object sender, KeyEventArgs e)
{
      Graphics g = Graphics.FromImage(canvas);
      if (e.KeyCode == Keys.Down && CurrentBlock.canMoveDown())
      {
            downKey = true;
            CurrentBlock.moveDown(g);
            if (rightKey && CurrentBlock.canMoveRight()) CurrentBlock.moveRight(g);
            else if (leftKey && CurrentBlock.canMoveLeft()) CurrentBlock.moveLeft(g);
      }
      else if (e.KeyCode== Keys.Down)
      {
            downKey = true;
            newBlock();
      }
      else if (e.KeyCode == Keys.Right && CurrentBlock.canMoveRight())
      {
            rightKey = true;
            CurrentBlock.moveRight(g);
            if (downKey && CurrentBlock.canMoveDown()) CurrentBlock.moveDown(g);
                else if (downKey) newBlock();
      }
      else if (e.KeyCode == Keys.Right)
      {
            rightKey = true;
            if (downKey && CurrentBlock.canMoveDown()) CurrentBlock.moveDown(g);
            else if (downKey) newBlock();
      }
      else if (e.KeyCode == Keys.Left && CurrentBlock.canMoveLeft())
      {
            leftKey = true;
            CurrentBlock.moveLeft(g);
            if (downKey && CurrentBlock.canMoveDown()) CurrentBlock.moveDown(g);
            else if (downKey) newBlock();
      }
      else if (e.KeyCode == Keys.Left)
      {
            leftKey = true;
            if (downKey && CurrentBlock.canMoveDown()) CurrentBlock.moveDown(g);
            else if (downKey) newBlock();
      }
      this.Refresh();
}

private void TetrisGame_KeyUp(object sender, KeyEventArgs e)
{
      if (e.KeyCode == Keys.Down)
            downKey = false;
      else if (e.KeyCode == Keys.Right)
            rightKey = false;
      else if (e.KeyCode == Keys.Left)
            leftKey = false;
}

Cannot capture KeyDown event for UP/DOWN-Arrow-Keys in Windows Form

3 Answers