return value of GetAsyncKeyState
<p>What is return value of GetAsyncKeyState ?</p>

<pre><code> public partial class Form1 : Form
    {
        [DllImport("User32.dll")]
        private static extern short GetAsyncKeyState(System.Windows.Forms.Keys key);
        private void button1_Click(object sender, EventArgs e)
        {
            short state = GetAsyncKeyState(Keys.D);
            switch (state)
            {
               // ?
            }
        }
    }
</code></pre>
