[Solved] deleting a detail does not update master

[Jim]

I have two grids in a master details scenario
The master class has an observable collection of the details class.
It generally works and if I cursor up and down the master grid the detail grid changes to reflect the correct details.
I implemented a StyleSelector such that the master rows that have detail entries show up in a different colour, this works OK.
However if I delete from the detail such that the master doesn't have any detail entries the grid doesn't pick it up.
Neither if I add a detail to a master that has no detail does that work.
If I reload the application things are then OK.
I assume it's something to do with INotifyCollectionChanged
Do I need to implement this somehow, if so I don;t know how to ?
Help !
Jim

[Jim]

I have reduced the problem to a small(ish) example.
You can cursor up/down the companies grid and the employees reflects the current company.
Also the style selector shows red if the company has no employees.
However if you select a company with employees and then delete all the employees for that company then the row doesn't change to red.
Again I suspect INotifyCollectionChanged might be the solution but not sure how !
Thanks
Jim

<UserControl x:Class="CollectionChangeNotification.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    xmlns:alloc="clr-namespace:CollectionChangeNotification"
    d:DesignHeight="480" d:DesignWidth="480" xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation" xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk">

    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.Resources>

            <alloc:RowStyle x:Key="rowStyle">
                <alloc:RowStyle.WithEmployeesStyle>
                    <Style TargetType="telerik:GridViewRow">
                        <Setter Property="Background" Value="LightCyan"/>
                    </Style>
                </alloc:RowStyle.WithEmployeesStyle>
                <alloc:RowStyle.WithoutEmployeesStyle>
                    <Style TargetType="telerik:GridViewRow">
                        <Setter Property="Background" Value="LightCoral" />
                    </Style>
                </alloc:RowStyle.WithoutEmployeesStyle>
            </alloc:RowStyle>

        </Grid.Resources>

        <Grid.RowDefinitions>
            <RowDefinition Height="244*" />
            <RowDefinition Height="236*" />
        </Grid.RowDefinitions>

        <telerik:RadGridView ItemsSource="{Binding}" RowStyleSelector="{StaticResource rowStyle}" AutoGenerateColumns="False" HorizontalAlignment="Left" Name="RadGridView1" VerticalAlignment="Bottom" Height="244" Width="480">
            <telerik:RadGridView.Columns>
                <telerik:GridViewDataColumn DataMemberBinding="{Binding CompanyName, Mode=TwoWay}" Header="Company Name"/>
            </telerik:RadGridView.Columns>
        </telerik:RadGridView>
        <telerik:RadGridView ItemsSource="{Binding ElementName=RadGridView1, Path=SelectedItem.Employees}" ShowInsertRow="True" CanUserInsertRows="True"  Grid.Row="1" HorizontalAlignment="Left" Name="RadGridView2" VerticalAlignment="Top" Height="236" Width="480" />
    </Grid>
</UserControl>

Imports System.ComponentModel
Imports System.Collections.ObjectModel
Imports Telerik.Windows.Controls

Partial Public Class MainPage
    Inherits UserControl

    Public Sub New()
        InitializeComponent()

        'Set up some data
        Dim electricCompany As Company = New Company("The Electric Company")
        Dim fred As New Employee("Fred Bloggs", 45)
        Dim anne As New Employee("Anne Smith", 20)
        electricCompany.Employees.Add(fred)
        electricCompany.Employees.Add(anne)

        Dim noEmployeeCompany As Company = New Company("The No Employee Company")

        Dim gasCompany As Company = New Company("The Gas Company")
        Dim peter As New Employee("Peter Perfect", 30)
        Dim george As New Employee("Georgie Porgie", 19)
        gasCompany.Employees.Add(peter)
        gasCompany.Employees.Add(george)

        Dim myCompanies As ObservableCollection(Of Company) = New ObservableCollection(Of Company)
        myCompanies.Add(electricCompany)
        myCompanies.Add(noEmployeeCompany)
        myCompanies.Add(gasCompany)

        DataContext = myCompanies

    End Sub

End Class
'**********************************************************************************************
Public Class Company

    Public Event PropertyChanged As PropertyChangedEventHandler

    Private Sub OnPropertyChanged([property] As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs([property]))
    End Sub

    Private m_CompanyName As String
    Private m_Employees As ObservableCollection(Of Employee)

    Public Property CompanyName As String
        Get
            Return m_CompanyName
        End Get
        Set(ByVal value As String)
            If m_CompanyName <> value Then
                m_CompanyName = value
                Me.OnPropertyChanged("CompanyName")
            End If
        End Set
    End Property

    Public Property Employees As ObservableCollection(Of Employee)
        Get
            Return m_Employees
        End Get
        Set(ByVal value As ObservableCollection(Of Employee))
            m_Employees = value
            Me.OnPropertyChanged("Employees")
        End Set
    End Property

    Public Sub New()
        MyBase.New()
        m_Employees = New ObservableCollection(Of Employee)
    End Sub

    Public Sub New(companyName As String)
        MyBase.New()
        m_CompanyName = companyName
        m_Employees = New ObservableCollection(Of Employee)
    End Sub

End Class
'**********************************************************************************************
Public Class Employee
    Public Event PropertyChanged As PropertyChangedEventHandler

    Private Sub OnPropertyChanged([property] As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs([property]))
    End Sub

    Private m_Name As String
    Private m_Age As Integer

    Public Property Name As String
        Get
            Return m_Name
        End Get
        Set(ByVal value As String)
            If m_Name <> value Then
                m_Name = value
                Me.OnPropertyChanged("Name")
            End If
        End Set
    End Property

    Public Property Age As Integer
        Get
            Return m_Age
        End Get
        Set(ByVal value As Integer)
            If m_Age <> value Then
                m_Age = value
                Me.OnPropertyChanged("Age")
            End If
        End Set
    End Property

    Public Sub New()
        MyBase.New()
    End Sub

    Public Sub New(name As String, age As Integer)
        MyBase.New()
        m_Name = name
        m_Age = age
    End Sub

End Class

'**********************************************************************************************
Public Class RowStyle
    Inherits StyleSelector
    Public Overrides Function SelectStyle(ByVal item As Object, ByVal container As DependencyObject) As Style
        Dim ans As Style = Nothing
        If TypeOf item Is Company Then
            Dim company As Company = TryCast(item, Company)
            If company.Employees.Count > 0 Then
                Return WithEmployeesStyle
            Else
                Return WithoutEmployeesStyle
            End If
        End If
        Return ans
    End Function
    Public Property WithEmployeesStyle() As Style
        Get
            Return m_WithEmployeesStyle
        End Get
        Set(ByVal value As Style)
            m_WithEmployeesStyle = value
        End Set
    End Property
    Private m_WithEmployeesStyle As Style
    Public Property WithoutEmployeesStyle() As Style
        Get
            Return m_WithoutEmployeesStyle
        End Get
        Set(ByVal value As Style)
            m_WithoutEmployeesStyle = value
        End Set
    End Property
    Private m_WithoutEmployeesStyle As Style
End Class

[Maya]

Hello Jim,

The row style selector will be invoked on change of the property of the item, not on change of the collection. What you may try is to expose a new property holding the count of the child items and set it on CollectionChanged event of the child collection. 
I am sending you a sample project illustrating the suggested approach.

Kind regards,
Maya
the Telerik team

[Jim]

Thanks for the reply, I will look at this when I get a spare moment.
Regards
Jim