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Tip of the Day
Language: VB7
Expertise: Intermediate
Nov 25, 2002



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Using multiple fields as value for the DropDownList control's items

Being an avid Access Programmer I have been frustrated with the limitation of VB DropDownLists to using only 1 field as the value. I found a way to simulate/work around this behavior with concatenation of several database fields at the query level to be my columns(i.e. Select KeyId1 + '~' + KeyId2 + '~' + KeyId3 as Keyval from...)

I use the combined keyval as the DropDown.DataValueField and then call my parse function after the user selects their choice on the DropDownList.SelectedItem.Value. I can now retrieve multiple column data from the DropDownList as I used to in Access without having to run an additional query. This may help other users that are frustrated with the limitations of the .NET combo/dropdownlist controls. In this particular application I have a series of nested dropdowns that depend on the selection of the previous dropdown.

This code is in the SelectedIndexChange event of the DropDownList1:

'(My Connection 'Cn' is already open)
Dim mysql As String

mysql = "select phaseid, description, PhaseID + '~' + RateHdrID + '~' + " _
    & "BillStatus AS KeyVal from tblphase where tblphase.clientid = '" & _
    Me.ClientCode.Text & "' and tblphase.jobid = '" & _
    Me.DropDownList1.SelectedItem.Value & "' and tblphase.active = 1"

Dim cmd2 As New SqlCommand(mysql, Cn)
Dim drPhase As SqlDataReader = cmd2.ExecuteReader _

CboPhase.DataSource = drPhase
CboPhase.DataTextField = "phaseid"
CboPhase.DataValueField = "KeyVal"
CboPhase.Items.Insert(0, "<---Select Phase-->")
After the postback on the CboPhase, in the SelectedIndexChange event I use this code:

If Me.CboPhase.SelectedIndex <> 0 Then
    Me.RateHdrID.Text = ParseVal(Me.CboPhase.SelectedItem.Value, 2)
    Me.BillStatus.Text = ParseVal(Me.CboPhase.SelectedItem.Value, 3)
End If
Where the ParseVal function returns the n-th piece of the value string:

Public Function ParseVal(ByVal MyString, ByVal KeyPos) As String
    ParseVal = ""
    If MyString <> "" Then
        Dim PosStart
        Dim PosEnd
        PosStart = InStr(1, MyString, "~")
        If PosStart > 0 Then
            Select Case KeyPos
                Case 1
                    ParseVal = Left(MyString, PosStart - 1)
                Case 2
                    PosEnd = InStr(PosStart + 1, MyString, "~")
                    ParseVal = Mid(MyString, PosStart + 1, _
                        PosEnd - PosStart - 1)
                Case 3
                    PosStart = InStr(PosStart + 1, MyString, "~")
                    ParseVal = Mid(MyString, PosStart + 1)
            End Select
        End If
    End If
End Function
Audrey Peters
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