How to Select Default Value/Text in Dropdownlist in C#

<asp:DropDownList ID="ddlSize" runat="server" OnDataBound="ddlSize_DataBound">
<asp:ListItem Value="1">S</asp:ListItem>
<asp:ListItem Value="2">M</asp:ListItem>
<asp:ListItem Value="3">L</asp:ListItem>
<asp:ListItem Value="4">XL</asp:ListItem>
<asp:ListItem Value="5">XXL</asp:ListItem>
</asp:DropDownList>

protected void ddlSize_DataBound(object sender, EventArgs e)
{
   if (ddlSize != null)
   {
      if (ddlSize.Items.FindByText("1") != null)
      {
         ddlSize.Items.FindByValue("1").Selected = true;
      }
   }
}

OR

protected void Page_Load(object sender, EventArgs e)
{
   if(!ispostback)
   {
      ddlSize.Items.FindByValue("1").Selected = true;
   }
}