Question

I have an ASP DataGrid and I’m applying sorting to it. Well, as I was looking at an example, they had a function similar in function, different in name, to:

Private Sub dgTasks_SortGrid(ByVal sender As Object, ByVal e As DataGridSortCommandEventArgs) Handles dgTasks.SortCommand
    Dim strSortDirection As String = Session("SortDir")
    If strSortDirection = Nothing Then
        strSortDirection = " ASC "
    Else
        If strSortDirection = " ASC " Then
            strSortDirection = " DESC "
        Else
            strSortDirection = " ASC "
        End If
    End If
    Session("SortDir") = strSortDirection
    BindData(e.SortExpression & strSortDirection)
End Sub

Well, me trying to make shortcuts and make things “easier” thought maybe this would be best:

Private Sub dgTasks_SortGrid(ByVal sender As Object, ByVal e As DataGridSortCommandEventArgs) Handles dgTasks.SortCommand
    If Session("SortDir") = Nothing Then
        Session("SortDir") = " ASC "
    Else
        If Session("SortDir") = " ASC " Then
            Session("SortDir") = " DESC "
        Else
            Session("SortDir") = " ASC "
        End If
    End If
    BindData(e.SortExpression & Session("SortDir"))
End Sub

However, as I was thinking about it, I figured maybe Session("SortDir") has to make a request everytime and it could have some affect or drawbacks. But I wasn’t sure. Does anyone have any links that would explain the best or preferred method. Thanks.

Answer 1

Looking up the Session value twice (one read and one write) rather than four times seems clearly better. The performance difference won’t be noticable by the user, but all those redundant lookups would make most programmers very uncomfortable! And there are some occasions where this kind of thing could make a noticable difference, depeding on the amount of data stored in the collection, and the type of lookup performed (hash table, binary search, sequential search, etc.), so it’s probably not a good habit to get into.