Blank option in ASP.NET DropDownList

I would like to create an blank option in DropDownList by default and don't use append to add options into the list. So, I bind the datasource first and then insert the blank option afterwards.

.aspx.cs

DropDownTenderNumber.DataSource = list;
DropDownTenderNumber.DataBind();
DropDownTenderNumber.Items.Insert(0, new ListItem("----PLEASE SELECT----", "0"));

Further, I use 'InitialValue' in RequiredFieldValidator to exclude the blank option.

.aspx