I have a simple MVVM project with design time data which works fine with both the main data and a listbox with user controls for each of the child items.
However when I instantiate the classes at run time, the the master data displays however the child data does not display (but the listbox has the correct number of items, however they don’t have any of the data displaying in the textboxes ).
I have noticed the constructor on Sport gets called far to many times, compared to what I’d expect (e.g. at run time, I’d expect it to be called only twice, but it seems to be called more than that).
I have class Person, and Sport. Every person can like multiple sports and have a favorite team.
I have a personViewModel & sportViewModel which inherit from viewModelBase.
Here is my VB.net Code
Imports System.Collections.ObjectModel
Public Class Person
Public Property Forename As String
Public Property Surname As String
Public Sports As New ObservableCollection(Of Sport)
End Class
Public Class Sport
Public Sub New()
Debug.WriteLine("test")
End Sub
Public Property SportName As String
Public Property FavouriteProfessionalTeam As String
End Class
Imports System.Collections.ObjectModel
Namespace ViewModel
Public Class PersonViewModel
Inherits ViewModel.ViewModelBase
Public Property Person1 As Person
Public Property SportViewModels As New ObservableCollection(Of SportViewModel)
Public Sub New()
LoadData()
End Sub
''' <summary>
''' Loads the data for the application.
''' </summary>
Private Sub LoadData()
If IsInDesignModeStatic Then
LoadDesignData()
Else
End If
End Sub
''' <summary>
''' Loads temporary data for use in the designer.
''' </summary>
Private Sub LoadDesignData()
Person1 = New Person
Person1.Forename = "Mickey Run Time"
Person1.Surname = "Mouse Run Time"
Person1.Sports.Add(New Sport With {.FavouriteProfessionalTeam = "Man Utd", .SportName = "Soccer"})
Person1.Sports.Add(New Sport With {.FavouriteProfessionalTeam = "Barcelona", .SportName = "Spanish Soccer"})
Person1.Sports.Add(New Sport With {.FavouriteProfessionalTeam = "Ulster", .SportName = "Rugby"})
For Each sport1 In Person1.Sports
Dim sportVm As New SportViewModel With {.Sport1 = sport1}
SportViewModels.Add(sportVm)
Next
End Sub
End Class
End Namespace
Namespace ViewModel
Public Class SportViewModel
Inherits ViewModel.ViewModelBase
Public Property Sport1 As New Sport
Public Property Person1 As Person
Public Sub New()
LoadData()
End Sub
''' <summary>
''' Loads the data for the application.
''' </summary>
Private Sub LoadData()
If IsInDesignModeStatic Then
LoadDesignData()
Else
' Debug.WriteLine(Sport1.SportName)
' Load the student data asynchronously
'StudentContextInstance = New StudentContext
'Dim loadop =
' StudentContextInstance.Load(StudentContextInstance.
' GetStudentsQuery(),
' AddressOf OnStudentsLoaded, Nothing)
End If
End Sub
''' <summary>
''' Loads temporary data for use in the designer.
''' </summary>
Private Sub LoadDesignData()
Sport1 = New Sport With {.SportName = "Design Time Name", .FavouriteProfessionalTeam = "Design Time Team"}
End Sub
End Class
End Namespace
Imports System.ComponentModel
Namespace ViewModel
Public Class ViewModelBase
Implements INotifyPropertyChanged
Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged
Private Shared _isInDesignMode As Boolean?
Public Shared ReadOnly Property IsInDesignModeStatic As Boolean
Get
If Not _IsInDesignMode.HasValue Then
_IsInDesignMode = DesignerProperties.GetIsInDesignMode(New DependencyObject)
End If
Return _IsInDesignMode.Value
End Get
End Property
Protected Sub OnPropertyChanged(ByVal propertyName As String)
' Send an event notification that the property changed
' This allows the UI to know when one of the items changes
If Not String.IsNullOrEmpty(propertyName) Then
RaiseEvent PropertyChanged(Me,
New PropertyChangedEventArgs(propertyName))
End If
End Sub
End Class
End Namespace
Here is the code behind for my wain window which sets up the MVVM for display
Imports System.Collections.ObjectModel
Imports WpfApplicationMVVMTest.ViewModel
Class MainWindow
Public Property Person1 As Person
Public Property SportViewModels As New ObservableCollection(Of SportViewModel)
Private Sub Button_Click_1(sender As Object, e As RoutedEventArgs)
Dim wndPerson As New PersonWindow
Person1 = New Person
Person1.Forename = "Donald"
Person1.Surname = "Duck"
Person1.Sports.Add(New Sport With {.FavouriteProfessionalTeam = "Man Utd", .SportName = "Soccer"})
Person1.Sports.Add(New Sport With {.FavouriteProfessionalTeam = "Barcelona", .SportName = "Spanish Soccer"})
For Each sport1 In Person1.Sports
Dim sportVm As New SportViewModel With {.Sport1 = sport1}
SportViewModels.Add(sportVm)
Next
Dim vm As New ViewModel.PersonViewModel
vm.SportViewModels = SportViewModels
vm.Person1 = Person1
wndPerson.DataContext = vm
wndPerson.Show()
End Sub
End Class
Here is the XAML Code
<Window
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" xmlns:ViewModel="clr-namespace:WpfApplicationMVVMTest.ViewModel"
xmlns:View="clr-namespace:WpfApplicationMVVMTest" mc:Ignorable="d" x:Class="PersonWindow"
Title="PersonWindow" Height="1114.8" Width="542">
<Window.Resources></Window.Resources>
<Window.DataContext>
<ViewModel:PersonViewModel />
</Window.DataContext>
<Grid>
<Grid x:Name="Grid1" HorizontalAlignment="Left" Margin="41,39,0,0" VerticalAlignment="Top">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Label Content="Forename:" Grid.Column="0" HorizontalAlignment="Left" Margin="3" Grid.Row="0" VerticalAlignment="Center"/>
<TextBox x:Name="ForenameTextBox" Grid.Column="1" HorizontalAlignment="Left" Height="23" Margin="3" Grid.Row="0" Text="{Binding Person1.Forename, Mode=TwoWay, NotifyOnValidationError=true, ValidatesOnExceptions=true}" VerticalAlignment="Center" Width="120"/>
<Label Content="Surname:" Grid.Column="0" HorizontalAlignment="Left" Margin="3" Grid.Row="1" VerticalAlignment="Center"/>
<TextBox x:Name="SurnameTextBox" Grid.Column="1" HorizontalAlignment="Left" Height="23" Margin="3" Grid.Row="1" Text="{Binding Person1.Surname, Mode=TwoWay, NotifyOnValidationError=true, ValidatesOnExceptions=true}" VerticalAlignment="Center" Width="120"/>
</Grid>
<ListBox Margin="41,108,59,753" ItemsSource="{Binding Path=SportViewModels}" >
<ListBox.ItemTemplate>
<DataTemplate>
<View:SportUserControl DataContext="{Binding}" Margin="5"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Window>
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:ViewModel="clr-namespace:WpfApplicationMVVMTest.ViewModel" x:Class="SportUserControl"
mc:Ignorable="d"
d:DesignHeight="600" d:DesignWidth="600">
<UserControl.Resources></UserControl.Resources>
<UserControl.DataContext>
<ViewModel:SportViewModel />
</UserControl.DataContext>
<Grid>
<Grid x:Name="Grid1" HorizontalAlignment="Left" Margin="31,26,0,0" VerticalAlignment="Top">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Label Content="Favourite Professional Team:" Grid.Column="0" HorizontalAlignment="Left" Margin="3" Grid.Row="0" VerticalAlignment="Center"/>
<TextBox x:Name="FavouriteProfessionalTeamTextBox" Grid.Column="1" HorizontalAlignment="Left" Height="23" Margin="3" Grid.Row="0" Text="{Binding Sport1.FavouriteProfessionalTeam, Mode=TwoWay, NotifyOnValidationError=true, ValidatesOnExceptions=true}" VerticalAlignment="Center" Width="120"/>
<Label Content="Sport Name:" Grid.Column="0" HorizontalAlignment="Left" Margin="3" Grid.Row="1" VerticalAlignment="Center"/>
<TextBox x:Name="SportNameTextBox" Grid.Column="1" HorizontalAlignment="Left" Height="23" Margin="3" Grid.Row="1" Text="{Binding Sport1.SportName, Mode=TwoWay, NotifyOnValidationError=true, ValidatesOnExceptions=true}" VerticalAlignment="Center" Width="120"/>
</Grid>
</Grid>
</UserControl>
Here is my design time image with 3 Sports displayed (as per my load design time data).
Here is my run time window with 2 sports displaying (although they have no data – which is the issue).
you are setting Datacontexts in your mark up and in code…remove the markup and stick to one pattern