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;  
   }   
}