rotected void btnSet_Click(object sender, EventArgs e)
    {
        foreach (ListItem item in lbCxLeft.Items)
        {
            if (item.Selected)
            {
                lbCxRight.Items.Add(item);
            }
        }
        foreach (ListItem item in lbCxRight.Items)
        {
            if (lbCxLeft.Items.FindByValue(item.Value) != null)
            {
                lbCxLeft.Items.Remove(item);
            }
        }
    }
    protected void btnSetAll_Click(object sender, EventArgs e)
    {
        foreach (ListItem item in lbCxLeft.Items)
        {
            lbCxRight.Items.Add(item);
        }
        lbCxLeft.Items.Clear();
    }
    protected void btnDel_Click(object sender, EventArgs e)
    {
        foreach (ListItem item in lbCxRight.Items)
        {
            if (item.Selected)
            {
                lbCxLeft.Items.Add(item);
            }
        }
        foreach (ListItem item in lbCxLeft.Items)
        {
            if (lbCxRight.Items.FindByValue(item.Value) != null)
            {
                lbCxRight.Items.Remove(item);
            }
        }
    }
    protected void btnDelAll_Click(object sender, EventArgs e)
    {
        foreach (ListItem item in lbCxRight.Items)
        {
            lbCxLeft.Items.Add(item);
        }
        lbCxRight.Items.Clear();
    }