Availability Seems Outta Control

Question

I have a ListDetails page that was behaving beautifully. I needed a property that showed the number of records when the DataControl_SeletionChanged event occurred, so I created the property "NumberInClass" and set it to equal the count of the records when the grid's selectionchanged fired. For no reason that I can figure out, none of the events in my EventsHandlers region fires now. The SiteRegistration_SelectionChanged event and ProgramRegistration_SelectionChanged works, but nothing else in the region does, and I mean nothing. I set break points on setting the priviate variables and I get nothing in the debugger.  SitesListDetail_ControlAvailable event or the other events (that are not commented out) in the region don't fire. The debugger doesn't break on the variables being created either.

Any thoughts anyone? Thanks... 

Imports System.Windows.Controls
Imports System.Windows.Data
Imports System.Text
Imports System.Collections
 
Namespace LightSwitchApplication
 
Public Class SitesListDetail
 
Private Const Data_Control As String = "ProgramRegistration"
Private WithEvents _dataControl As DataGrid = Nothing
Private _selectedCount As Integer '= 0
 
#Region " Event Handlers "
 
 
		Private Sub SitesListDetail_ControlAvailable(send As Object, e As ControlAvailableEventArgs)
			'we know that the control is a grid, but we use TryCast, just in case 
			_dataControl = TryCast(e.Control, DataGrid)
 
			'if the cast failed, just leave, there's nothing more we can do here 
			If (_dataControl Is Nothing) Then Return
 
			'set the property on the grid that allows multiple selection 
			_dataControl.SelectionMode = DataGridSelectionMode.Extended
		End Sub
 
 
		'Private Sub Sites_SelectionChanged()
			'Me.NumberInClass = Me.ProgramRegistration.Count
		'End Sub
 
		'Private Sub SiteRegistration_SelectionChanged()
		'			Me.NumberInClass = Me.ProgramRegistration.Count
		'End Sub
 
		Private Sub DataControl_SelectionChanged() Handles _dataControl.SelectionChanged
				_selectedCount = _dataControl.SelectedItems.Count
			If _selectedCount > 0 Then
				Me.FindControl("AddNewAttendance").IsVisible = True
				Me.FindControl("Tardy").IsVisible = True
				Me.FindControl("ExcusedAbsence").IsVisible = True
				Me.FindControl("UnexcusedAbsence").IsVisible = True
				Me.FindControl("Rainout").IsVisible = True
				Me.NumberInClass = Me.ProgramRegistration.Count
			Else
				Me.FindControl("AddNewAttendance").IsVisible = False
				Me.FindControl("Tardy").IsVisible = False
				Me.FindControl("ExcusedAbsence").IsVisible = False
				Me.FindControl("UnexcusedAbsence").IsVisible = False
				Me.FindControl("Rainout").IsVisible = False
			End If
		End Sub
 
#End Region

Answer 1

I don't see anywhere in this code where you subscribe the SitesListDetail_ControlAvailable method as an event handler. It should look like this:

AddHandler Me.FindControl(SitesListDetail.Data_Control).ControlAvailable, AddressOf Me.SitesListDetail_ControlAvailable

either in your SitesListDetail_Created method or SitesListDetail_InitializeDataWorkspace method.

---

Justin Anderson, LightSwitch Development Team

Answer 2

I am not sure if that line of code was accidentally removed or not, but I do know that everything was working prior to adding the property I mentioned. In any event, adding the code you suggested to the SitesListDetail_InitializeDataWorkspace method has everything performing as expected. Thank you so much for taking a look and sharing your insight.