Search a 2D array for a value <=

[Kingadasouth96]

I am working on an application that calculates a shipping price based on the amount ordered. I have a 2D array (or so I believe) that I am searching, however it only yields any results when I search for an exact number. I would like to set it so when I search a value between 1 and 10 I get a $15 for shipping. Right now I have to enter 1 to receive the $15 shipping, 11 for $10, and so on. Below is what I have so far.

Public Class frmMain

    Private strItems(,) As String = {{"1", "15"},
                                    {"11", "10"},
                                    {"51", "5"},
                                    {"101", "0"}}



    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
        Me.Close()
    End Sub

    Private Sub txtordered_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtOrdered.KeyPress
        ' allows the text box to accept numbers and the Backspace key

        If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> ControlChars.Back Then
            e.Handled = True
        End If
    End Sub

    Private Sub txtordered_TextChanged(sender As Object, e As EventArgs) Handles txtOrdered.TextChanged
        lblShipping.Text = String.Empty
    End Sub

    Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click





        Dim strSearchForId As String
        Dim intRow As Integer

        strSearchForId = txtOrdered.Text

        Do Until intRow > strItems.GetUpperBound(0) OrElse
            strSearchForId = strItems(intRow, 0)
            intRow += 1
        Loop
        If intRow <= strItems.GetUpperBound(0) Then
            Dim intPrice As Integer
            Integer.TryParse(strItems(intRow, 1), intPrice)
            lblShipping.Text = intPrice.ToString("C0")

        End If


    End Sub

End Class

I have tried playing with the columns and rows to no avail. Some assistance would be greatly appreciated.
I am using a textbox to enter in my search value and a label to display the shipping cost.

[Shaggy Hiker]

You do have a 2D array, but you almost certainly would be better off without one. So, why do you have a 2D array? Is there some requirement that you have one?

One issue is that the values are clearly numbers, and you are already fighting with that. For one thing, since the array is strings, you always have to convert to integer for comparisons, which is inefficient. For another, you are using a Textbox for entry and have to add that code to restrict it to numbers. That isn't really safe, though, because copy and paste will bypass what you have done, since the KeyPress event won't fire. Better would be to use a NumericUpDown control that already only allows numbers, and returns a number (though a Decimal) from the .Value property.

A 2D array is ok if you will never be changing the size. If you are changing the size, you would probably be better off making a small class or structure with two members, then creating a sorted list of those objects. The two members would be something like Threshold and Value. Another option would be to use a SortedDictionary, which would be a bit easier. What you'd have to do is iterate through the keys, and as soon as you find one that is higher than the value you are seeking, you'd take the value associated with that key.

[Kingadasouth96]

I have been hearing that a lot, that 2D arrays are becoming less and less used. Its for my advanced CIS class. The book touches on multidimensional array but does not cover one quite like this. Thank you for the lead however I will try and see what I can do.

[Shaggy Hiker]

There are drawbacks to multi-D arrays, especially these days, but somewhat in earlier times. The main problem is that they are really touch to change the size on. VB only allowed resizing the final dimension of the array. If you wanted to resize any other dimension you had to do it yourself by creating a new array of the new size, and copying over data from the old array to the new array as you saw fit. Not totally horrible, but not so easy, either.

Now, with the introduction of generics in 2005, you have a bunch of collections that are quick, easy, and quite efficient, to resize, such as the List(of T). However, the List(of T) is only one dimension and that's all you can have. It is so quick, easy, and efficient, though, that it is often easier to create some custom class or structure and just maintain a List of those. Furthermore, there are lots of cases where that is the right thing to do, because the 2D array doesn't really capture the concept you are trying to capture. A 2D array makes a lot of sense if you have a table, though the Datatable might be better for such a thing. In this case, you don't really have a 2D array so much as you have a set of item pairs. The pairs consist of a threshold and a value. If X gets above the threshold, then use the value associated with it. Conceptually, that sounds more like an object that has the threshold and a value, to me, rather than a 2D grid of values.

The SortedDictionary would just be a shortcut to the same result. Normally, dictionaries are using the key to look up the value, but there is no reason not to use them as a key associated with a value, and if they are sorted, they'd serve the purpose you need. After all, you need that threshold to be sorted, so sorted keys would do just as well.

[Kingadasouth96]

Got it figured out tho. I hope I don't have to use these but I got it working.

  Private items As String(,) = {{"1", "15"},
                                     {"11", "10"},
                                     {"51", "5"},
                                     {"101", "0"}}

    Private Sub Amount_TxtBox_TextChanged(sender As System.Object, e As System.EventArgs) Handles Amount_TxtBox.TextChanged

    End Sub

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub GetShipping_But_Click(sender As System.Object, e As System.EventArgs) Handles CalcTotal_But.Click
        Dim itemCost As Integer
        Dim shippingCost As Integer

        If Not Integer.TryParse(Me.Amount_TxtBox.Text, itemCost) Then
            MsgBox("Please enter a valid amount!", MsgBoxStyle.Critical Or MsgBoxStyle.OkOnly, "Error in item cost")
            Exit Sub
        End If

        shippingCost = GetShipping(itemCost)

        Me.ItemShipping_Lbl.Text = shippingCost.ToString()
        Me.TotalCost_TxtBox.Text = CalcTotal(itemCost, shippingCost).ToString()

    End Sub

    Private Function GetShipping(ByVal itemAmount As Integer) As Integer
        Dim amount As Integer = 0

        Integer.TryParse(Me.Amount_TxtBox.Text, amount)

        For item As Integer = 0 To (items.GetUpperBound(0)) Step +1

            If (items.GetLength(0)) <= (item + 1) Then
                Return CInt(items(items.GetLength(0) - 1, 1))
            End If

            If amount >= CInt(items(item, 0)) And amount < CInt(items(item + 1, 0)) Then
                Return CInt(items(item, 1))
            End If
        Next

        Return 0
    End Function

    Private Function CalcTotal(ByVal itemCost As Integer, ByVal shippingCost As Integer) As Integer
        Return itemCost + shippingCost
    End Function
End Class

Had to make classes. But still kept the 2D array so this should be acceptable.
Thank you for all the information, I really can't learn enough.

[Shaggy Hiker]

Nobody can. There is always more to learn for all of us.

[Kingadasouth96]

I think that's exactly the pure essence of why I enjoy it.