固定位置排序
sql.OrderBy(d => System.Data.Entity.SqlServer.SqlFunctions.CharIndex(((int)d.state).ToString(), "0,1,2,3,-1"))
可以看作是这样地
sql.OrderBy(d => System.Data.Entity.SqlServer.SqlFunctions.CharIndex(d.id.ToString(), "0,1,2,3,-1"))
