DropDownList has a DataSource() proterty. After giving a source to the drop down list you can bind it afterwards. For an example code check here;
DropDownList ddlNumbers = new DropDownList();
Hashtable myNumbers = New Hashtable();
myNumbers.Add("1","One");
myNumbers.Add("2","Two");
myNumbers.Add("3","Three");
myNumbers.Add("4","Four");
ddlNumbers.DataSource = myNumbers;
ddlNumbers.DataValueField = "Key";
ddlNumbers.DataTextField = "Value";
ddlNumbers.DataBind();
Good luck