I created a CRUD operation and in that, I get an error while trying to delete a record:

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=472540 for information on understanding and handling optimistic concurrency exceptions.

I created this action method for deleting a record:

[HttpPost]
public ActionResult Delete(tblMember objMember)
{
    _memberContext.Entry(objMember).State = EntityState.Deleted;

    int a = _memberContext.SaveChanges();

    if (a > 0)
    {
        TempData["DeleteMessage"] = "<script>alert('Data Deleted')</script>";
    }
    else
    {
        TempData["DeleteMessage"] = "<script>alert('Data Not Deleted')</script>";
    } 

    return RedirectToAction("MemberList");
}