As a fast solution to your requirement (in case you are not planing to use JavaScript which could be a valid solution) you can clear you result message variable "ViewBag.result" in the start of your search method logic
public search()
{
ViewBag.result = "";
\\....search logic
return View("Index");
}
And I think you need to clear the variable in your other methods also "Insert/Update/Delete" in order not to have the same previous action result message.