Re: how to add "Select" item in combobox in silverlight 3

Question

Hi,
 
     I want to add default item like "--Select--" in combobox for silverlight 3 for both static/dynamic population of combo box.
Here is the sample code.Please Help.

 List<date> _date = new List<date>()
            {
                new date() {Name="Mins"},
                new date() {Name="Hour"},
                new date() {Name="Day"},
                new date() {Name="Week"},
                new date() {Name="Month"},
                new date() {Name="Year"}

            };
            cmbPerweek1.ItemsSource = _date;
           // cmbPerweek1.Items.Add("--Select Time Interval--");
            cmbPerweek1.Items.Insert(0,"--Select Time Interval--");
            cmbPerweek1.SelectedIndex = 0;

This is one type and another dropdown is loaded from Service.How to add for that too.When it run the Application it displays
"Operation not supported on read-only collection."..


Thanks in Advance.