I changed ListItem's Value start with capital (True|False), and it works fine. You might want to give a try.
<asp:DropDownList ID="ExcludedDropDown" runat="server"
SelectedValue='<%# Bind("IsExcluded") %>'>
<asp:ListItem Value="True" Text="Include"></asp:ListItem>
<asp:ListItem Value="False" Text="Exclude"></asp:ListItem>
</asp:DropDownList>
Here is how I test
public class Something
{
public string Some { get; set; }
public bool IsExcluded { get; set; }
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
var collections = new List<Something>
{
new Something {Some = "One", IsExcluded = true},
new Something {Some = "Two", IsExcluded = false},
};
GridView1.DataSource = collections;
GridView1.DataBind();
}
}