var dict = new Dictionary<string,string>();
dict.Add("A","123");
dict.Add("B","456");
dict.Add("C","789");
dict.Add("D","000");
var list = new List<Dictionary<string,string>>(); //pretty much like a DataTable
list.Add(dict); //more than one dict in the list
//ddl is a dropdownlist
ddl.DataSource = list
ddl.DataTextField ="[A]";
ddl.DataValueField ="[C]";
ddl.DataBind();
You should bind your dictionary, not list. Something like this :
var dict = new Dictionary<string,string>();
dict.Add("A","123");
ddl.DataSource = dict
ddl.DataTextField ="Key";
ddl.DataValueField ="Value";
ddl.DataBind();