Bind dropdown with selected value during edit time in MVC

ViewBag.ddlprincepal = new SelectList(objentity.ddlPrincipal(), "PrincipalID", "PrincipalName");

ViewBag.ddlprincepalselected = new SelectListItem { Text = inventoryDetailobj[0].PrincipalName, Value = (inventoryDetailobj[0].PrincipalID).ToString(),Selected=true };