Text box allow only date in DD/MM/YYYY fromate

<asp:textbox runat="server" id="TextBox1" xmlns:asp="#unknown" />
<asp:customvalidator runat="server" controltovalidate="TextBox1" errormessage="Date was in incorrect format" onservervalidate="CustomValidator1_ServerValidate" xmlns:asp="#unknown" />

protected void CustomValidator1_ServerValidate(object sender, ServerValidateEventArgs e)
{
    DateTime d;
    e.IsValid = DateTime.TryParseExact(e.Value, "dd/MM/yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out d);
}

/*If you want to allow other formats */

DateTime.TryParseExact(e.Value, new[] { "dd/MM/yyyy", "yyyy-MM-dd" }, CultureInfo.InvarinatCulture, DateTimeStyles.None, out d);

public void Button1_Click(object sender, EventArgs e)
{
        DateTime Test;
        if (DateTime.TryParseExact(TextBox1.Text, "MM/dd/yyyy", null, DateTimeStyles.None, out Test) == true)
            Response.Write("Date is Valid");
        else
            Response.Write("Invalid Date");
}