C#如何在keydown事件里判断按下的是左shift还是右shift

 public partial class Form1 : Form 
 
    { 
 
        [System.Runtime.InteropServices.DllImport("user32.dll")] 
 
        private static extern short GetAsyncKeyState(Keys vKey); 
 
        public Form1() 
 
        { 
 
            InitializeComponent(); 
 
        } 
 
        private void Form1_KeyDown(object sender, KeyEventArgs e) 
 
        { 
 
            if (e.KeyCode == Keys.ShiftKey) 
 
            { 
 
                if (Convert.ToBoolean(GetAsyncKeyState(Keys.LShiftKey))) 
 
                    MessageBox.Show("Left"); 
 
                if (Convert.ToBoolean(GetAsyncKeyState(Keys.RShiftKey))) 
 
                    MessageBox.Show("Right"); 
 
            } 
 
        } 
 
    }