WinForms 自定义控件：为什么方向键不引发 OnKeyDown 事件？

Question

This is a dummy custom control. The entire source is at the bottom. If I place the control on an empty form (no weird things like key preview, etc, just the default, empty, untouched form), and press some keys, weirdly, arrow keys do not raise OnKeyDown . Why?

If I keep pressing 'A'.

Process: A
Key down: A
Process: A
Key down: A
Process: A
Key down: A

If I keep pressing the Space bar.

Process: Space
Key down: Space
Process: Space
Key down: Space
Process: Space
Key down: Space
Process: Space

If I keep pressing the Down arrow.

Process: Down
Process: Down
Process: Down
Process: Down
Process: Down
Process: Down

Is overriding the ProcessCmdKey the only and best way to handle arrow key inputs? I cannot use the OnKeyUp event, because it is raised only once, but users would keep pressing the arrow key to continuously scroll down, not just once when they release the arrow key.

public class MyControl : Control
{
    protected override void OnKeyDown(KeyEventArgs e)
    {
        base.OnKeyDown(e);
        Debug.WriteLine("Key down: " + e.KeyCode);
    }

    protected override void OnKeyUp(KeyEventArgs e)
    {
        base.OnKeyUp(e);
        Debug.WriteLine("Key up: " + e.KeyCode);
    }

    protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
    {
        Debug.WriteLine("Process: " + keyData.ToString());
        return base.ProcessCmdKey(ref msg, keyData);
    }
}

Answer 1

Overriding ProcessCmdKey I think is the right way to go here. I can't fully explain why OnKeyDown isn't being called, but there's nothing particularly wrong with overriding ProcessCmdKey , and if it works, it works.