I am trying to set up a datagrid combobox column to get the display member
given the value member when the datasource is a BindingList(Of T).
I expanded on a MS example for the BindingList, and am attempting to use
reflection to get a property value from the instance that represents the type
'T' - in this case, an instance of the Part class.  My complete code is
below.  It fails with a TargetException in the GetText method when I actually
call 'propertyInfo.GetValue'.

Any help on what I am doing wrong would be awesome.

Thanks, John

Option Explicit On
Option Strict On
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Reflection
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Public Class Form1

   Private randomNumber As New Random()
   Private bs2 As BindingSource
   Private strDisplay As String = "DisplayMember"
   Private strValueMember As String = "ValueMember"
   ' Declare a new BindingListOfT with the Part business object.
   'Private WithEvents listOfParts As GenericBindingList(Of
Generic2ValBusinessObject(Of Integer, String))
   Private WithEvents listOfParts As BindingList(Of Part)
   Dim properties As PropertyDescriptorCollection =
TypeDescriptor.GetProperties(listOfParts)

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

       InitializeListOfParts()
       ListBox1.DataSource = listOfParts
       ListBox1.DisplayMember = "PartName"
       '
       bs2 = New BindingSource(listOfParts, "")

       With Me.ComboBox2
           .DisplayMember = "PartName"
           .ValueMember = "PartNumber"
           .DataSource = bs2
       End With

       Me.Label1.Text = bs2.Position.ToString
       'Me.Label3.Text = Me.GetText(bs2,
listOfParts(bs2.Position).ValueMember)
   End Sub

   Private Sub InitializeListOfParts()

       listOfParts = New BindingList(Of Part)

       With listOfParts
           ' Allow new parts to be added, but not removed once committed.  
   
           .AllowNew = True
           .AllowRemove = False

           ' Raise ListChanged events when new parts are added.
           .RaiseListChangedEvents = True

           ' Do not allow parts to be edited.
           .AllowEdit = False

           ' Add a couple of parts to the list.

           listOfParts.Add(New Part(1234, "Widget"))
           listOfParts.Add(New Part(5647, "Gadget"))

       End With

   End Sub

   ' Create a new part from the text in the two text boxes.
   Private Sub listOfParts_AddingNew(ByVal sender As Object, _
       ByVal e As AddingNewEventArgs) Handles listOfParts.AddingNew
       e.NewObject = New Part(Integer.Parse(TextBox2.Text), TextBox1.Text)

   End Sub

   ' Add the new part unless the part number contains
   ' spaces. In that case cancel the add.
   Private Sub button1_Click(ByVal sender As Object, _
       ByVal e As EventArgs) Handles Button1.Click

       Dim newPart As Part = listOfParts.AddNew()

       If newPart.PartName.Contains(" ") Then
           MessageBox.Show("Part names cannot contain spaces.")
           listOfParts.CancelNew(listOfParts.IndexOf(newPart))
       Else
           TextBox2.Text = randomNumber.Next(9999).ToString()
           TextBox1.Text = "Enter part name"
       End If

   End Sub

   <STAThread()> _
   Shared Sub Main()
       Application.EnableVisualStyles()
       Application.Run(New Form1())

   End Sub

   Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As Object, ByVal
e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
       Me.Label1.Text = bs2.Position.ToString
       Me.Label3.Text = Me.GetText(bs2, listOfParts(bs2.Position).PartNumber)
   End Sub

   Private Function GetText(ByVal bs As BindingSource, ByVal ValueMember As
Object) As String

       Dim strOut As String = String.Empty
       Try

           Dim genericType As Type = bs.DataSource.GetType 'BindingList(Of
Part)

           Dim openGenericType As Type = genericType.GetGenericTypeDefinition

           Dim typeParams() As Type = genericType.GetGenericArguments

           'BindingList(Of T)
           'Has only one parameter
           Dim struc As Type = typeParams(0) 'Part type

           Dim valProp As PropertyInfo = struc.GetProperty("DisplayText")

           Dim args() As Object = {ValueMember, bs.DataSource}

           'THE OFFENDING CODE
           'THROWS TARGETEXCEPTION
           Dim o As Object = valProp.GetValue(bs.DataSource, args)

           If Not o Is Nothing Then
               strOut = o.ToString
           End If

       Catch ex As Exception
           MessageBox.Show(ex.ToString)
       End Try

       Return strOut

   End Function

End Class

' A simple business object for example purposes.
Public Class Part
   Private name As String
   Private number As Integer

   Public Sub New()
   End Sub

   Public Sub New(ByVal numberForPart As Integer, ByVal nameForPart As
String)
       PartName = nameForPart
       PartNumber = numberForPart

   End Sub

   Public Property PartName() As String
       Get
           Return name
       End Get
       Set(ByVal value As String)
           name = Value
       End Set
   End Property

   Public Property PartNumber() As Integer
       Get
           Return number
       End Get
       Set(ByVal value As Integer)
           number = Value
       End Set
   End Property

   Public ReadOnly Property DisplayText(ByVal _PartNumber As Integer, ByVal
BL As BindingList(Of Part)) As String
       Get

           If BL IsNot Nothing Then

               For n As Integer = 0 To BL.Count - 1

                   Dim Inst As Part = DirectCast(BL(n), Part)
                   If Inst.PartNumber = _PartNumber Then
                       Return Inst.PartName
                   End If
               Next n
           End If

           Return String.Empty
       End Get
   End Property

End Class

-- <Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class Form1
   Inherits System.Windows.Forms.Form

   'Form overrides dispose to clean up the component list.
   <System.Diagnostics.DebuggerNonUserCode()> _
   Protected Overrides Sub Dispose(ByVal disposing As Boolean)
       If disposing AndAlso components IsNot Nothing Then
           components.Dispose()
       End If
       MyBase.Dispose(disposing)
   End Sub

   'Required by the Windows Form Designer
   Private components As System.ComponentModel.IContainer

   'NOTE: The following procedure is required by the Windows Form Designer
   'It can be modified using the Windows Form Designer.  
   'Do not modify it using the code editor.
   <System.Diagnostics.DebuggerStepThrough()> _
   Private Sub InitializeComponent()
       Me.ListBox1 = New System.Windows.Forms.ListBox
       Me.Button1 = New System.Windows.Forms.Button
       Me.TextBox1 = New System.Windows.Forms.TextBox
       Me.TextBox2 = New System.Windows.Forms.TextBox
       Me.ComboBox2 = New System.Windows.Forms.ComboBox
       Me.Label1 = New System.Windows.Forms.Label
       Me.Label3 = New System.Windows.Forms.Label
       Me.Label4 = New System.Windows.Forms.Label
       Me.Label6 = New System.Windows.Forms.Label
       Me.SuspendLayout()
       '
       'ListBox1
       '
       Me.ListBox1.FormattingEnabled = True
       Me.ListBox1.Location = New System.Drawing.Point(32, 26)
       Me.ListBox1.Name = "ListBox1"
       Me.ListBox1.Size = New System.Drawing.Size(175, 95)
       Me.ListBox1.TabIndex = 0
       '
       'Button1
       '
       Me.Button1.Location = New System.Drawing.Point(514, 120)
       Me.Button1.Name = "Button1"
       Me.Button1.Size = New System.Drawing.Size(75, 23)
       Me.Button1.TabIndex = 1
       Me.Button1.Text = "Save Part"
       Me.Button1.UseVisualStyleBackColor = True
       '
       'TextBox1
       '
       Me.TextBox1.Location = New System.Drawing.Point(479, 42)
       Me.TextBox1.Name = "TextBox1"
       Me.TextBox1.Size = New System.Drawing.Size(144, 20)
       Me.TextBox1.TabIndex = 2
       Me.TextBox1.Text = "Enter a name"
       '
       'TextBox2
       '
       Me.TextBox2.Location = New System.Drawing.Point(479, 82)
       Me.TextBox2.Name = "TextBox2"
       Me.TextBox2.Size = New System.Drawing.Size(144, 20)
       Me.TextBox2.TabIndex = 3
       Me.TextBox2.Text = "8434"
       '
       'ComboBox2
       '
       Me.ComboBox2.FormattingEnabled = True
       Me.ComboBox2.Location = New System.Drawing.Point(32, 177)
       Me.ComboBox2.Name = "ComboBox2"
       Me.ComboBox2.Size = New System.Drawing.Size(234, 21)
       Me.ComboBox2.TabIndex = 5
       '
       'Label1
       '
       Me.Label1.AutoSize = True
       Me.Label1.Location = New System.Drawing.Point(215, 225)
       Me.Label1.Name = "Label1"
       Me.Label1.Size = New System.Drawing.Size(39, 13)
       Me.Label1.TabIndex = 6
       Me.Label1.Text = "Label1"
       '
       'Label3
       '
       Me.Label3.AutoSize = True
       Me.Label3.Location = New System.Drawing.Point(215, 257)
       Me.Label3.Name = "Label3"
       Me.Label3.Size = New System.Drawing.Size(39, 13)
       Me.Label3.TabIndex = 8
       Me.Label3.Text = "Label3"
       '
       'Label4
       '
       Me.Label4.AutoSize = True
       Me.Label4.Font = New System.Drawing.Font("Microsoft Sans Serif",
8.25!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point,
CType(0, Byte))
       Me.Label4.Location = New System.Drawing.Point(56, 225)
       Me.Label4.Name = "Label4"
       Me.Label4.Size = New System.Drawing.Size(138, 13)
       Me.Label4.TabIndex = 9
       Me.Label4.Text = "BindingSource Position"
       '
       'Label6
       '
       Me.Label6.AutoSize = True
       Me.Label6.Font = New System.Drawing.Font("Microsoft Sans Serif",
8.25!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point,
CType(0, Byte))
       Me.Label6.Location = New System.Drawing.Point(56, 257)
       Me.Label6.Name = "Label6"
       Me.Label6.Size = New System.Drawing.Size(96, 13)
       Me.Label6.TabIndex = 11
       Me.Label6.Text = "Get Text Result"
       '
       'Form1
       '
       Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
       Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
       Me.ClientSize = New System.Drawing.Size(781, 351)
       Me.Controls.Add(Me.Label6)
       Me.Controls.Add(Me.Label4)
       Me.Controls.Add(Me.Label3)
       Me.Controls.Add(Me.Label1)
       Me.Controls.Add(Me.ComboBox2)
       Me.Controls.Add(Me.TextBox2)
       Me.Controls.Add(Me.TextBox1)
       Me.Controls.Add(Me.Button1)
       Me.Controls.Add(Me.ListBox1)
       Me.Name = "Form1"
       Me.Text = "Form1"
       Me.ResumeLayout(False)
       Me.PerformLayout()

   End Sub
   Friend WithEvents ListBox1 As System.Windows.Forms.ListBox
   Friend WithEvents Button1 As System.Windows.Forms.Button
   Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
   Friend WithEvents TextBox2 As System.Windows.Forms.TextBox
   Friend WithEvents ComboBox2 As System.Windows.Forms.ComboBox
   Friend WithEvents Label1 As System.Windows.Forms.Label
   Friend WithEvents Label3 As System.Windows.Forms.Label
   Friend WithEvents Label4 As System.Windows.Forms.Label
   Friend WithEvents Label6 As System.Windows.Forms.Label
 

End Class
John