Retrieve SharePoint List Data and bind this to a dropdownlist

To bind the drop down list data with a field from the SharePoint list you can use the below code methods:-
Method 1

       
if (!Page.IsPostBack)
        {
            using (SPSite site = new ("http://yoursharepointsite"))
            {
                using (SPWeb web = site.OpenWeb())
                {
                    SPList list = web.Lists["NameOfYourList"];
                    dropSite.DataSource = list.Items;
                    dropSite.DataValueField = "Title"; // List field holding value - first column is called Title anyway!
                    dropSite.DataTextField = "Title"; // List field holding name to be displayed on page 
                    dropSite.DataBind();
                }
            }
        }

Method 2:- Using SPDataSource