Add Default Item to DropDownList Dynamically

How to add a default item as 'N/A' to drop down list and set selected?

[sourcecode language="csharp"]
gnList.DataSourceID = "GNDS";
gnList.DataTextField = "Name";
gnList.DataValueField = "Id";
gnList.DataBind();
gnList.Items.Insert(0, new ListItem("N/A", "0"));
[/sourcecode]

Another way

[sourcecode language="csharp"]
gnList.Items.Add(new ListItem("N/A", "0"));
gnList.DataSourceID = "GNDS";
gnList.DataTextField = "Name";
gnList.DataValueField = "Id";
gnList.DataBind();
gnList.Items.FindByValue("0").Selected = true;
[/sourcecode]