Insert into your data table dont go for fresh insert. Do this after fetch from db
SqlDataAdapter da1 = new SqlDataAdapter(strng, con);
DataTable dt = new DataTable();
da1.Fill(dt);
DataRow toInsert = dt.NewRow();
row["EName"] = "--Select--";
row["ID"] = "--Select--";
dt.Rows.InsertAt(toInsert, 0);
ddLogo.DataSource = dt;
ddLogo.DataTextField = "Ename";
ddLogo.DataValueField = "ID";
ddLogo.DataBind();