VLC Player plugin for C# cannot set volume for the first video

I try to play video with vlc plugin in C# like this tutorial http://ift.tt/1CJQvXQ . I want to reduce audio volume. I set volume in vlc Properties to 0 and paste axVLCPlugin21.audio.Volume = 10; to every where in code. The first play of video not reduce volume . It's 100% volume . My code can reduce when I click change to secound video only.

How to set reduce volume for the first play video in vlc plugin with C# ?

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            axVLCPlugin21.audio.Volume = 10;
         }

        private void Form1_Load(object sender, EventArgs e)
        {
            DirectoryInfo di = new DirectoryInfo("H:/Movie");
            FileInfo[] fi = di.GetFiles("*.mp4");

            foreach(FileInfo curFile in fi)
            {
                listBox1.Items.Add(curFile.Name);
                axVLCPlugin21.playlist.add("file:///"+ curFile.FullName);

            }
                axVLCPlugin21.audio.Volume = 10;

        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            int selIndex = listBox1.SelectedIndex;
            axVLCPlugin21.playlist.playItem(selIndex);
            axVLCPlugin21.audio.Volume = 10;
        }

        private void axVLCPlugin21_MediaPlayerEndReached(object sender, EventArgs e)
        {

            if (listBox1.SelectedIndex < (listBox1.Items.Count - 1))
            {

                axVLCPlugin21.playlist.next();
                listBox1.SelectedIndex += 1;
                listBox1.Update();
                axVLCPlugin21.audio.Volume = 10;
            }
            else
            {

                axVLCPlugin21.playlist.playItem(0);
                listBox1.SelectedIndex = 0;
                listBox1.Update();
                axVLCPlugin21.audio.Volume = 10;
            }
        }

    }