add time click button with comma

I have created sample refer the below code.

HTML

<div>
    <asp:ListBox runat="server" ID="lstPerson" SelectionMode="Multiple">
        <asp:ListItem Text="Nurullo" Value="1" />
        <asp:ListItem Text="Sadriddin" Value="2" />
        <asp:ListItem Text="Firuz" Value="3" />
    </asp:ListBox>
    <br />
    <asp:ListBox runat="server" ID="lstFruit" SelectionMode="Multiple">
        <asp:ListItem Text="Apple" Value="1" />
        <asp:ListItem Text="Orange" Value="2" />
        <asp:ListItem Text="Cherry" Value="3" />
        <asp:ListItem Text="Melon" Value="4" />
    </asp:ListBox>
    <br />
    <asp:Button Text="Save" runat="server" OnClick="Save" />
</div>

Code

protected void Save(object sender, EventArgs e)
{
    string person = string.Empty;
    string fruit = string.Empty;
    foreach (ListItem persons in lstPerson.Items)
    {
        if (persons.Selected)
        {
            person += persons.Value + ","; ;
        }
    }

    foreach (ListItem fruits in lstFruit.Items)
    {
        if (fruits.Selected)
        {
            fruit += fruits.Text + ",";
        }
    }

    person = person.Remove(person.Length - 1);
    fruit = fruit.Remove(fruit.Length - 1);
    //Code for saving the data to db.
}