How to bind Dropdownlist with whole english characters in ASP.NET C#

I want to say that how to add English alphabets at run time in DropdownList. A intermediate programmer know that each char contain a ASCII value like 65 is a ASCII value of letter 'A'. Similarly again 66 to 90 is a ASCII value of Letter B to Z.  So add a DropdownList in the design page also bind with Alphabet public property. Look like this:

Source page:
<asp:DropDownList ID="Letters" DataSource='<%# Alphabet %>' runat="server" />

Code Behind Page:
public partial class Bynamejobsearch : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            DataBind();
        }
    }
    private List<char> _Alphabet;
    protected List<char> Alphabet
    {
        get
        {
            if (_Alphabet == null)
            {
                _Alphabet = new List<char>();
                for (int i = 65; i < 91; i++)
                {
                    _Alphabet.Add(Convert.ToChar(i));
                }
            }
            return _Alphabet;
        }
    }
}
In this program i have a list of type char. Use for loop which is start from 65 to 90. Add this char in the list one by one.