stop bell ctrl-a (winforms)

any ideas stop component bell sounding ctrl-a used name calm winforms application?

here's problem. emanate winforms project. place calm box form supplement following eventuality handler form grant ctrl-a name calm textbox (no matter control focus).

void form1_keydown(object sender, keyeventargs e)
{
    (e.keycode == keys.a && e.modifiers == keys.control)
    {
        system.diagnostics.debug.writeline("control pressed.");
        txtcontent.selectionstart = 0;
        txtcontent.selectionlength = txtcontent.text.length;
        txtcontent.focus();
        e.handled = true;
    }
}

it works, nonetheless notwithstanding e.handled = true, component bell sound each ctrl-a pressed.

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thanks reply.

keypreview form set loyal - nonetheless doesn't stop component bell sounding - problem i'm perplexing solve - annoying.