How can you clear GridView by clicking a button?

protected void Page_Load(object sender, EventArgs e)
    {
        List<string> s = new List<string>();
        s.Add("vb");
        s.Add("csharp");
        GridView1.DataSource = s;
        GridView1.DataBind();

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        GridView1.DataSource = null;
        GridView1.DataBind();

    }