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How to properly bind multiple ViewModels when using DataTemplateSelector [duplicate]

This question already has answers here:
How to use DataTemplateSelector with ContentControl to display different controls based on the view-model?
(2 answers)
Closed 4 years ago.
I'm trying to write a simple dialog that would accept a value in a SpinEdit or a text in a TextEdit. I'm using multiple VMs and I made a selector that should view a proper control based on the logic in the c++/cli file.
XAML:
xmlns:local="clr-namespace:asd"
Title="{Binding Path=Title, Mode=OneTime}"
<dx:DXWindow.Resources>
<DataTemplate x:Key="TInputValueVM" DataType="{x:Type local:TInputValueVM}">
<dxe:SpinEdit Height="23" Width="200"
Text="{Binding Value, Mode=TwoWay}"
Mask="{Binding Mask, Mode=OneWay}"
MaxLength="{Binding Path=InputLength}" />
</DataTemplate>
<DataTemplate x:Key="TInputTextVM" DataType="{x:Type local:TInputTextVM}">
<dxe:TextEdit Height="23" Width="200"
Text="{Binding Value, Mode=TwoWay}"
MaskType="RegEx" Mask="{Binding Mask, Mode=OneWay}"
MaxLength="{Binding Path=InputLength}"/>
</DataTemplate>
<local:PropertyDataTemplateSelector x:Key="templateSelector"
DataTemplate_Value="{StaticResource TInputValueVM}"
DataTemplate_Text="{StaticResource TInputTextVM}" />
</dx:DXWindow.Resources>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<StackPanel Grid.Row="0" >
<Label x:Uid="Label" MinHeight="24" MinWidth="60" Content="Value" />
<ContentControl Content="{Binding Path=Whoami}" ContentTemplateSelector="{StaticResource templateSelector}" />
</StackPanel>
<StackPanel Grid.Row="1" x:Uid="OKCancel_Buttons" Orientation="Horizontal" HorizontalAlignment="Right" VerticalAlignment="Bottom">
<Button Height="23" x:Name="OK_Button" Click="OK_Click" Content="OK" IsDefault="True" HorizontalAlignment="Right" MinWidth="95" />
<Button Height="23" x:Name="Cancel_Button" Click="Cancel_Click" Content="Cancel" HorizontalAlignment="Right" MinWidth="95" />
</StackPanel>
</Grid>
In c# I have a base VM and two VMS that extend it, one for values and one for text. The rest of the properties stay the same.
C#
namespace asd
{
public class TInputBaseVM : ViewModelBase
{
private string m_sTitle;
private string m_sMask;
private int m_nInputLenght;
private string m_sWhoami;
public TInputBaseVM(string A_sTitle, string A_sMask, int A_nInputLength)
{
m_sTitle = A_sTitle;
m_sMask = A_sMask;
m_nInputLenght = A_nInputLength;
}
protected string Title
{
get { return m_sTitle; }
set { SetProperty(ref m_sTitle, value, () => Title); }
}
protected string Mask
{
get { return m_sMask; }
set { SetProperty(ref m_sMask, value, () => Mask); }
}
protected int InputLength
{
get { return m_nInputLenght; }
set { SetProperty(ref m_nInputLenght, value, () => InputLength); }
}
protected string Whoami
{
get { return m_sWhoami; }
set { SetProperty(ref m_sWhoami, value, () => Whoami); }
}
}
public class TInputValueVM : TInputBaseVM
{
public TInputValueVM(string A_sTitle, string A_sMask, int A_nInputLength, double A_nValue) : base(A_sTitle, A_sMask, A_nInputLength)
{
Value = A_nValue;
Whoami = "Value";
}
private double m_nValue;
public double Value
{
get { return m_nValue; }
set { SetProperty(ref m_nValue, value, () => Value); }
}
}
public class TInputTextVM : TInputBaseVM
{
public TInputTextVM(string A_sTitle, string A_sMask, int A_nInputLength, string A_sValue) : base(A_sTitle, A_sMask, A_nInputLength)
{
Value = A_sValue;
Whoami = "Text";
}
private string m_sValue;
public string Value
{
get { return m_sValue; }
set { SetProperty(ref m_sValue, value, () => Value); }
}
}
public class PropertyDataTemplateSelector : DataTemplateSelector
{
public DataTemplate DataTemplate_Value { get; set; }
public DataTemplate DataTemplate_Text { get; set; }
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
var selector = item as string;
if(selector == "Value")
return DataTemplate_Value;
return DataTemplate_Text;
}
}
}
In c++/cli I create an object of a proper VM and I'd like the WPF to automatically update the view to either spinedit or textedit, however I'm not sure how to properly bind the properties from the C#. If I explicitly type 'Value' in the Content property of the ContentControl then it displays the spinEdit but I don't know how to bind it so it automatically takes the correct property.
EDIT: I'm adding c++/cli code to show how I choose different VMs
C++/cli:
bool TSignalNumberPositionDialogCLR::StartDialog(TSignalNumberPositionSupport& A_Attributes, HWND A_hwndParent, LPTSTR String)
{
try
{
TInputValueVM ^oExchange_Value;
TInputTextVM ^oExchange_Text;
int inputFormat = A_Attributes.GetInputFormat();
if(inputFormat)
oExchange_Text = gcnew TInputTextVM(gcnew System::String(A_Attributes.GetTitle()), gcnew System::String(A_Attributes.GetMask()),
A_Attributes.GetInputLength(), gcnew System::String(A_Attributes.GetInitialText()));
else
oExchange_Value = gcnew TInputValueVM(gcnew System::String(A_Attributes.GetTitle()), gcnew System::String(A_Attributes.GetMask()),
A_Attributes.GetInputLength(), A_Attributes.GetInitialValue());
Dialogs::TSignalNumberPositionDialog^ dialog = gcnew Dialogs::TSignalNumberPositionDialog();
if(inputFormat)
dialog->DataContext = oExchange_Text;
else
dialog->DataContext = oExchange_Value;
dialog->ShowDialog();
if(dialog->DialogResult)
{
CString nValue;
if(inputFormat)
nValue = oExchange_Text->Value;
else
nValue = ((Decimal)oExchange_Value->Value).ToString("F2", CultureInfo::InvariantCulture);
A_Attributes.UpdateValue(nValue, String, A_Attributes.GetInputLength());
return true;
}
return false;
}
catch(Exception^ e)
{
e;
}
}
based on the 'inputFormat' variable I want to display different controls in the dialog.
EDIT: Based on #Clemens comments I got rid of the selector sectionand the x:Key property in the DataTemplates. I changed the content opf the Content property to Content="{Binding}" and it somehow works. The moment I create a VM it selects the correct one.

Based on your comment. Let me improve my answer. As you are facing issue in VM selection. so plesae concentrate how I assigned VM to datatemplate. Although it is done in very basic way, you can handle it if you you are using MVVM packages.
I have created 2 data template and 2 vms and each vm is bound to datatemplate. To verify, I have a combobox, which will select datatemplate based on selected value.
Here is Sample VM
public class VM : System.ComponentModel.INotifyPropertyChanged
{
private string title;
private SolidColorBrush background;
public string Title { get => title; set { title = value; RaisePropertyChanged(); } }
public SolidColorBrush Background { get => background; set { background = value; RaisePropertyChanged(); } }
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string name = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
}
public class VM1: VM
{
public VM1()
{
Title = "This is VM1";
Background = Brushes.Yellow;
}
}
public class VM2: VM
{
public VM2()
{
Title = "This is VM2";
Background = Brushes.Orange;
}
}
Now check for resources
<local:VM1 x:Key="VM1"/>
<local:VM2 x:Key="VM2"/>
<DataTemplate x:Key="DT1">
<Grid DataContext="{StaticResource VM1}">
<TextBlock Text="{Binding Title}" Background="{Binding Background}"/>
</Grid>
</DataTemplate>
<DataTemplate x:Key="DT2">
<Grid DataContext="{StaticResource VM2}">
<TextBlock Text="{Binding Title}" Background="{Binding Background}"/>
</Grid>
</DataTemplate>
<Style TargetType="ContentControl" x:Key="contentStyle">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=cmbo, Path=SelectedValue}" Value="Template1">
<Setter Property="ContentTemplate" Value="{StaticResource DT1}" />
</DataTrigger>
<DataTrigger Binding="{Binding ElementName=cmbo, Path=SelectedValue}" Value="Template2">
<Setter Property="ContentTemplate" Value="{StaticResource DT2}" />
</DataTrigger>
</Style.Triggers>
</Style>
and finally I have combobox and content control just to verify
<ComboBox Name="cmbo"/>
<ContentControl Style="{StaticResource contentStyle}"/>
where cmbo.ItemsSource = new List { "Template1", "Template2" };
Hope you got the point

Changing the ViewModel's property from another ViewModel

I have the ListBox on my MainView.xaml, selecting the Item forces the ContentControl to display different UserControls. I use Caliburn.Micro library in this propgram. Here's some code:
<ListBox Grid.Row="1" Grid.Column="1" x:Name="ItemsListBox" SelectedItem="0" ItemsSource="{Binding Items}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<TextBlock Grid.Row="2" Grid.Column="1" Text="{Binding TextBlock1Text}" x:Name="TextBlock1"/>
<ContentControl Grid.Row="3" Grid.Column="1" Content="{Binding ElementName=ItemsListBox, Path=SelectedItem.Content}" />
The MainViewModel.cs:
private string _name;
public string Name
{
get => _name;
set
{
_name = value;
NotifyOfPropertyChange(() => Name);
}
}
private string _textBlock1Text;
public string TextBlock1Text
{
get => _textBlock1Text;
set
{
_textBlock1Text = value;
NotifyOfPropertyChange(() => TextBlock1Text);
}
}
public MainViewModel()
{
TextBlock1Text = "Test";
Items = new ObservableCollection<ItemsModel>()
{
new ItemsModel { Name="Useless", Content=null },
new ItemsModel { Name="TextChangerViewModel", Content=new TextChangerViewModel(TextBlock1Text) }
};
}
public ObservableCollection<ItemsModel> Items { get; set; }
The ItemsModel.cs:
public class ItemsModel
{
public string Name { get; set; }
public object Content { get; set; }
}
And finally the TextChangerViewModel.cs:
public class TextChangerViewModel : Conductor<object>
{
private string _textBlock1Text;
public string TextBlock1Text
{
get => _textBlock1Text;
set
{
_textBlock1Text = value;
NotifyOfPropertyChange(() => TextBlock1Text);
}
}
public TextChangerViewModel(string textBlock1Text) //passing parameter from another ViewModel
{
TextBlock1Text = textBlock1Text;
}
}
So, the main question is how to change the TextBlock1Text (and the Text value of TextBlock in .xaml as well) in the MainViewModel.cs from the TextChangerViewModel.cs? I was thinking about using something like NotifyCollectionChanged on my Items ObservableCollection, but it work with collection of ItemsModel, not with the VM's, so I'm stuck here.
I'm also not sure if having public object Content { get; set; } in ItemsModel.cs is a good thing if I'm targeting the MVVM pattern, but I don't know the other way to do it (I'm very new to MVVM).
UPD
I'm looking for the property-changing way because I need to change the TextBlock1Text Text from another UserControl. Suppose I have the button on my TextChangerView.xaml: <Button Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Content="Change da text" cal:Message.Attach="ChangeTextButton"/>
And after the click on it I want the text on the parental MainView.xaml to change. But the thing is, I don't know how to change properties in this case, as I wrote above why.

Change the the binding of textblox1 to reference the selected item.
<TextBlock Grid.Row="2" Grid.Column="1" Text="{Binding ElementName=ItemsListBox, Path=SelectedItem.Name}" x:Name="TextBlock1"/>
or
<TextBlock Grid.Row="2" Grid.Column="1" Text="{Binding ElementName=ItemsListBox, Path=SelectedItem.Content.TextBlock1Text}" x:Name="TextBlock1"/>

WPF Tabcontrol (TabItem Content is not appearing)

I implemented a TabControl with Closable TabItems in my App. For this, I am using a Collection which I fill with the SubMenuItems of MenuItem "Öffne", which are bound to ICommands in the MainViewModel.
So if I click on MenuItem "Open Tab1", then the header of Tab 1 is created, but I can not see any content. The content of the TabItem is shown AFTER I click on the Header of the TabItem. But I want it to be shown directly when the TabItem is "created" without any need of clicking on the header. Closing the TabItems from the "X" button works fine.
I looked at a couple of examples and tried a ContentTemplate, but it didn't work (Maybe I made something wrong?).
I Hope you can tell me what i have done wrong or show me a good example.
Thanks in advance!
Here are my code snippets:
MainWindow.XAML:
<Window.Resources>
<vm:MainViewModel x:Key="viewModel"/>
</Window.Resources>
<TabControl Background="#FFE5E5E5" ItemsSource="{Binding TabControlViews}" SelectedItem="{Binding CurrentTabItem}" Margin="0,21,0,0">
<TabControl.ItemTemplate>
<DataTemplate>
<DockPanel Width="120">
<TextBlock Text="{Binding Header}"/>
<Button
Command="{Binding ParameterizedCommand, Source={StaticResource viewModel}}"
CommandParameter="{Binding Header, RelativeSource={RelativeSource AncestorType={x:Type TabItem}}}"
Content="X"
Cursor="Hand"
DockPanel.Dock="Right"
Focusable="False"
FontFamily="Courier"
FontSize="9"
FontWeight="Bold"
Margin="0,1,0,0"
Padding="0"
VerticalContentAlignment="Bottom"
Width="16" Height="16" />
<ContentPresenter
Content="{Binding Path=DisplayName}"
VerticalAlignment="Center" />
</DockPanel>
</DataTemplate>
</TabControl.ItemTemplate>
<!--<TabControl.ContentTemplate>
<DataTemplate>
</DataTemplate>
</TabControl.ContentTemplate>-->
<TabControl.Resources>
<DataTemplate x:Name="test" DataType="{x:Type vm:MenueVM}">
<cu:MenueSearch/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:FieldPointsVM}">
<cu:FieldPointsSearch/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:DataTransferVM}">
<cu:DataTransfer/>
</DataTemplate>
</TabControl.Resources>
</TabControl>
MainWindow.cs:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
var vm = (MainViewModel)Resources["viewModel"];
this.DataContext = vm;
}
}
MainViewModel.cs:
public MainViewModel()
{
TabControlViews = new ObservableCollection<BaseViewModel>();
_menueVM = new MenueVM("Menüpunkte", "Menue");
_fieldVM = new FieldPointsVM("Feldpunkte", "FieldPoint");
_dataVM = new DataTransferVM("DatenTransfer", "DataTransfer");
ParameterizedCommand = new RelayCommand(DoParameterizedCommand);
}
private void DoParameterizedCommand(object parameter)
{
if (parameter.ToString() == "App.ViewModel.MenueVM")
{
TabControlViews.Remove(_menueVM);
}
else if (parameter.ToString() == "App.ViewModel.FieldPointsVM")
{
TabControlViews.Remove(_fieldVM);
}
else if (parameter.ToString() == "App.ViewModel.DataTransfer")
{
TabControlViews.Remove(_dataVM);
}
}
private ICommand _parameterizedCommand;
public ICommand ParameterizedCommand
{
get
{
return _parameterizedCommand;
}
set
{
_parameterizedCommand = value;
}
}
private TabItem _propCurrentTabItem;
public TabItem CurrentTabItem
{
get
{
return _propCurrentTabItem;
}
set
{
_propCurrentTabItem = value;
}
}
private ObservableCollection<BaseViewModel> _TabControlViews = new ObservableCollection<BaseViewModel>();
public ObservableCollection<BaseViewModel> TabControlViews
{
get
{
return _TabControlViews;
}
set
{
_TabControlViews = value;
OnPropertyChanged();
}
}
public ICommand OpenMenupunkteCommand
{
get
{
return new BaseCommand(OpenMenuPunkte);
}
}
public ICommand OpenFeldpunkteCommand
{
get
{
return new BaseCommand(OpenFeldpunkte);
}
}
public ICommand OpenDataTransferCommand
{
get
{
return new BaseCommand(OpenDataTransfer);
}
}
private void OpenMenuPunkte()
{
if (!TabControlViews.Contains(_menueVM))
{
TabControlViews.Add(_menueVM);
}
}
private void OpenFeldpunkte()
{
if (!TabControlViews.Contains(_fieldVM))
{
TabControlViews.Add(_fieldVM);
}
}
private void OpenDataTransfer()
{
if (!TabControlViews.Contains(_dataVM))
{
TabControlViews.Add(_dataVM);
}
}
MenueVM.cs
public class MenueVM : BaseViewModel
{
public MenueVM()
{
//Here are some actions done for Data, but I think they are unimportant for this question
}
public MenueVM(string header, string content)
{
Header = header;
Content = content;
}
private string _header;
public string Header
{
get
{
return _header;
}
set
{
_header = value;
}
}

Still time to post an answer?
Try this :
XAML:
<TabControl ItemsSource="{Binding....}" IsSynchronizedWithCurrentItem="True">
<!-- style, template, ... -->
</TabControl>
CS:
//Adding your viewModel to your ObservableCollection<> TabControlViews
TabControlViews.Add(_viewModelToAdd);
ICollectionView collectionView = CollectionViewSource.GetDefaultView(TabControlViews);
if (collectionView != null)
{
collectionView.MoveCurrentTo(_viewModelToAdd);
//And this is because you don't want your tabItem to be selected :
collectionView.MoveCurrentToPrevious();
}
Found in the downloadable DemoMVVMApp here : https://msdn.microsoft.com/en-us/magazine/dd419663.aspx#id0090030
I've also spent a huge amount of time to solve this problem... ;-)

The problem is that your tab is been created, but it´s not been selected. So, in addition to calling
TabControlViews.Add(_dataVM)
, you should also update your CurrentTabItem
CurrentTabItem = _dataVM;
and bind your TabControl SelectedItem property to your CurrentTabItem, like this:
<TabControl ItemsSource="{Binding TabControlViews}" SelectedItem="{Binding CurrentTabItem}">
Also, if you remove a TabItem and want to get back to the last one, you have to call
CurrentTabItem = TabControlViews.LastOrDefault();

Nested Data Binding using MVVM in WPF not working

I am not able to figure out why my third Nested DataBinding in WPF is not working. I am using Entity Framework and Sql Server 2012 and following are my entities. An Application can have more than one accounts. There is an Accounts Table and an Applications Table.
ENTITIES
1. Applications
2. Accounts
VIEWMODELS
1. ApplicationListViewModel
2. ApplicationViewModel
3. AccountListViewModel
4. AccountViewModel
In my usercontrol I am trying to do following:
1. Use combobox to select an application using ApplicationListViewModel (Working)
2. Upon selected application display all accounts in datagrid (Working)
3. Upon selected account display details information about a particular account.(Does not show details of the selected account)
<UserControl.Resources>
<vm:ApplicationListViewModel x:Key="AppList" />
</UserControl.Resources>
<StackPanel DataContext="{Binding Source={StaticResource AppList}}">
<Grid>
<Grid.RowDefinitions>
...
</Grid.ColumnDefinitions>
<StackPanel Grid.Row="0" Grid.Column="0">
<GroupBox Header="View all">
<StackPanel>
<!-- All Applications List -->
<ComboBox x:Name="cbxApplicationList"
ItemsSource="{Binding Path=ApplicationList}"
DisplayMemberPath="Title" SelectedValuePath="Id"
SelectedItem="{Binding Path=SelectedApplication, Mode=TwoWay}"
IsSynchronizedWithCurrentItem="True" />
<!-- Selected Application Accounts -->
<DataGrid x:Name="dtgAccounts" Height="Auto" Width="auto" AutoGenerateColumns="False"
DataContext="{Binding SelectedApplication.AccountLVM}"
ItemsSource="{Binding Path=AccountList}"
SelectedItem="{Binding SelectedAccount, Mode=TwoWay}" IsSynchronizedWithCurrentItem="True">
<DataGrid.Columns>
<DataGridTextColumn Header="Title" Binding="{Binding Path=Title}"></DataGridTextColumn>
</DataGrid.Columns>
</DataGrid>
</StackPanel>
</GroupBox>
</StackPanel>
<StackPanel Grid.Row="0" Grid.Column="1" >
<GroupBox x:Name="grpBoxAccountDetails" Header="New Account" >
<!-- Selected Account Details -->
<!-- DataContext binding does not appear to work -->
<StackPanel DataContext="{Binding SelectedApplication.AccountLVM.SelectedAccount}" >
<Grid>
<Grid.RowDefinitions>
...
</Grid.ColumnDefinitions>
<TextBlock x:Name="lblApplication" Grid.Row="0" Grid.Column="0" >Application</TextBlock>
<ComboBox x:Name="cbxApplication" Grid.Row="0" Grid.Column="1"
DataContext="{Binding Source={StaticResource AppList}}"
ItemsSource="{Binding ApplicationList}"
DisplayMemberPath="Title" SelectedValuePath="Id"
SelectedValue="{Binding SelectedApplication.AccountLVM.SelectedAccount.ApplicationId}">
</ComboBox>
<TextBlock x:Name="lblTitle" Grid.Row="0" Grid.Column="0" >Title</TextBlock>
<TextBox x:Name="txtTitle" Grid.Row="0" Grid.Column="1" Height="30" Width="200"
Text="{Binding Title}" DataContext="{Binding Mode=OneWay}"></TextBox>
<Button Grid.Row="1" Grid.Column="0" Command="{Binding AddAccount}">Add</Button>
</Grid>
</StackPanel>
</GroupBox>
</StackPanel>
</Grid>
</StackPanel>
ApplicationListViewModel
class ApplicationListViewModel : ViewModelBase
{
myEntities context = new myEntities();
private static ApplicationListViewModel instance = null;
private ObservableCollection<ApplicationViewModel> _ApplicationList = null;
public ObservableCollection<ApplicationViewModel> ApplicationList
{
get
{
return GetApplications();
}
set {
_ApplicationList = value;
OnPropertyChanged("ApplicationList");
}
}
//public ObservableCollection<ApplicationViewModel> Cu
private ApplicationViewModel selectedApplication = null;
public ApplicationViewModel SelectedApplication
{
get
{
return selectedApplication;
}
set
{
selectedApplication = value;
OnPropertyChanged("SelectedApplication");
}
}
//private ICommand showAddCommand;
public ApplicationListViewModel()
{
this._ApplicationList = GetApplications();
}
internal ObservableCollection<ApplicationViewModel> GetApplications()
{
if (_ApplicationList == null)
_ApplicationList = new ObservableCollection<ApplicationViewModel>();
_ApplicationList.Clear();
foreach (Application item in context.Applications)
{
ApplicationViewModel a = new ApplicationViewModel(item);
_ApplicationList.Add(a);
}
return _ApplicationList;
}
public static ApplicationListViewModel Instance()
{
if (instance == null)
instance = new ApplicationListViewModel();
return instance;
}
}
ApplicationViewModel
class ApplicationViewModel : ViewModelBase
{
private myEntities context = new myEntities();
private ApplicationViewModel originalValue;
public ApplicationViewModel()
{
}
public ApplicationViewModel(Application acc)
{
//Initialize property values
this.originalValue = (ApplicationViewModel)this.MemberwiseClone();
}
public ApplicationListViewModel Container
{
get { return ApplicationListViewModel.Instance(); }
}
private AccountListViewModel _AccountLVM = null;
public AccountListViewModel AccountLVM
{
get
{
return GetAccounts();
}
set
{
_AccountLVM = value;
OnPropertyChanged("AccountLVM");
}
}
internal AccountListViewModel GetAccounts()
{
_AccountLVM = new AccountListViewModel();
_AccountLVM.AccountList.Clear();
foreach (Account i in context.Accounts.Where(x=> x.ApplicationId == this.Id))
{
AccountViewModel account = new AccountViewModel(i);
account.Application = this;
_AccountLVM.AccountList.Add(account);
}
return _AccountLVM;
}
}
AccountListViewModel
class AccountListViewModel : ViewModelBase
{
myEntities context = new myEntities();
private static AccountListViewModel instance = null;
private ObservableCollection<AccountViewModel> _accountList = null;
public ObservableCollection<AccountViewModel> AccountList
{
get
{
if (_accountList != null)
return _accountList;
else
return GetAccounts();
}
set {
_accountList = value;
OnPropertyChanged("AccountList");
}
}
private AccountViewModel selectedAccount = null;
public AccountViewModel SelectedAccount
{
get
{
return selectedAccount;
}
set
{
selectedAccount = value;
OnPropertyChanged("SelectedAccount");
}
}
public AccountListViewModel()
{
this._accountList = GetAccounts();
}
internal ObservableCollection<AccountViewModel> GetAccounts()
{
if (_accountList == null)
_accountList = new ObservableCollection<AccountViewModel>();
_accountList.Clear();
foreach (Account item in context.Accounts)
{
AccountViewModel a = new AccountViewModel(item);
_accountList.Add(a);
}
return _accountList;
}
public static AccountListViewModel Instance()
{
if (instance == null)
instance = new AccountListViewModel();
return instance;
}
}
AccountViewModel. I am eliminating all other initialization logic aside in viewmodel for simplicity.
class AccountViewModel : ViewModelBase
{
private myEntites context = new myEntities();
private AccountViewModel originalValue;
public AccountViewModel()
{
}
public AccountViewModel(Account acc)
{
//Assign property values.
this.originalValue = (AccountViewModel)this.MemberwiseClone();
}
public AccountListViewModel Container
{
get { return AccountListViewModel.Instance(); }
}
public ApplicationViewModel Application
{
get;
set;
}
}
Edit1:
When I data bind to view the details of the SelectedAccount with textbox it doesn't show any text.
1. Able to databind to ApplicationListViewModel to Combobox.
2. Successfully Bind to view AccountList based upon SelectedApplication
3. Unable to Bind to SelectedAcount in the AccountListViewModel.
I think in the following line it doesn't show any details about the selected account. I have checked all databinding syntax. In the properties I am able to view appropriate DataContext and bind to the properties. But it doesn't show any text. When I select each individual record in the DataGrid I am able to debug the call and select the object but somehow that object is not being shown in the textbox at the very end.
DataContext="{Binding SelectedApplication.AccountLVM.SelectedAccount}"
Edit2:
Based upon the suggestion in the comment below I tried snoop and was able to see the title textbox row highlighted in red color. I am trying to change the binding Path property and datacontext but still not working. When I tried to click on the "Delve Binding Expression" it gave me unhandled exception. I don't know what that means if as it came from Snoop.
Edit3:
I have taken screenshots of DataContext Property for the StackPanel for the Account Details section and the text property of the textbox.
Solution:
Based upon suggestions below I have made following changes to my solution and made it way more simple. I made it unnecessarily complex.
1. AccountsViewModel
2. AccountViewModel
3. ApplicationViewModel
Now I have created properties as SelectedApplication, SelectedAccount all in just one AccountsViewModel. Removed all complex DataContext syntax and now there is just one DataContext in the xaml page.
Simplified code.
class AccountsViewModel: ViewModelBase
{
myEntities context = new myEntities();
private ObservableCollection<ApplicationViewModel> _ApplicationList = null;
public ObservableCollection<ApplicationViewModel> ApplicationList
{
get
{
if (_ApplicationList == null)
{
GetApplications();
}
return _ApplicationList;
}
set
{
_ApplicationList = value;
OnPropertyChanged("ApplicationList");
}
}
internal ObservableCollection<ApplicationViewModel> GetApplications()
{
if (_ApplicationList == null)
_ApplicationList = new ObservableCollection<ApplicationViewModel>();
else
_ApplicationList.Clear();
foreach (Application item in context.Applications)
{
ApplicationViewModel a = new ApplicationViewModel(item);
_ApplicationList.Add(a);
}
return _ApplicationList;
}
//Selected Application Property
private ApplicationViewModel selectedApplication = null;
public ApplicationViewModel SelectedApplication
{
get
{
return selectedApplication;
}
set
{
selectedApplication = value;
this.GetAccounts();
OnPropertyChanged("SelectedApplication");
}
}
private ObservableCollection<AccountViewModel> _accountList = null;
public ObservableCollection<AccountViewModel> AccountList
{
get
{
if (_accountList == null)
GetAccounts();
return _accountList;
}
set
{
_accountList = value;
OnPropertyChanged("AccountList");
}
}
//public ObservableCollection<AccountViewModel> Cu
private AccountViewModel selectedAccount = null;
public AccountViewModel SelectedAccount
{
get
{
return selectedAccount;
}
set
{
selectedAccount = value;
OnPropertyChanged("SelectedAccount");
}
}
internal ObservableCollection<AccountViewModel> GetAccounts()
{
if (_accountList == null)
_accountList = new ObservableCollection<AccountViewModel>();
else
_accountList.Clear();
foreach (Account item in context.Accounts.Where(x => x.ApplicationId == this.SelectedApplication.Id))
{
AccountViewModel a = new AccountViewModel(item);
_accountList.Add(a);
}
return _accountList;
}
}
XAML Side
<UserControl.Resources>
<vm:AccountsViewModel x:Key="ALVModel" />
</UserControl.Resources>
<StackPanel DataContext="{Binding Source={StaticResource ALVModel}}" Margin="0,0,-390,-29">
<StackPanel>
<ComboBox x:Name="cbxApplicationList"
ItemsSource="{Binding Path=ApplicationList}"
DisplayMemberPath="Title" SelectedValuePath="Id"
SelectedItem="{Binding Path=SelectedApplication, Mode=TwoWay}"
IsSynchronizedWithCurrentItem="True"></ComboBox>
<DataGrid x:Name="dtgAccounts" Height="Auto" Width="auto"
AutoGenerateColumns="False"
ItemsSource="{Binding Path=AccountList}"
SelectedItem="{Binding SelectedAccount, Mode=TwoWay}"
IsSynchronizedWithCurrentItem="True" >
<DataGrid.Columns>
<DataGridTextColumn Header="Title" Binding="{Binding Path=Title}"></DataGridTextColumn>
<DataGridTextColumn Header="CreatedDate" Binding="{Binding Path=CreatedDate}"></DataGridTextColumn>
<DataGridTextColumn Header="LastModified" Binding="{Binding Path=LastModifiedDate}"></DataGridTextColumn>
</DataGrid.Columns>
</DataGrid>
</StackPanel>
<StackPanel Height="Auto" Width="300" HorizontalAlignment="Left" DataContext="{Binding Path=SelectedAccount}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="30"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100"></ColumnDefinition>
<ColumnDefinition Width="200"></ColumnDefinition>
</Grid.ColumnDefinitions>
<TextBlock x:Name="lblTitle" Grid.Row="0" Grid.Column="0" >Title</TextBlock>
<TextBox x:Name="txtTitle" Grid.Row="0" Grid.Column="1" Height="30" Width="200"
Text="{Binding Title}"></TextBox>
</Grid>
</StackPanel>
</StackPanel>
I didn't understood MVVM concept properly. I tried to build everything modular and in the end I screwed it up.

I suspect your problem is related to the fact you are returning a new ObservableCollection every time you call the setter for AccountLVM, and you are not raising your PropertyChange notification, so any existing bindings do not get updated
public AccountListViewModel AccountLVM
{
get
{
return GetAccounts();
}
set
{
_AccountLVM = value;
OnPropertyChanged("AccountLVM");
}
}
internal AccountListViewModel GetAccounts()
{
_AccountLVM = new AccountListViewModel();
_AccountLVM.AccountList.Clear();
foreach (Account i in context.Accounts.Where(x=> x.ApplicationId == this.Id))
{
AccountViewModel account = new AccountViewModel(i);
account.Application = this;
_AccountLVM.AccountList.Add(account);
}
return _AccountLVM;
}
I find your bindings very confusing and hard to follow, however I think whenever this gets evaluated
DataContext="{Binding SelectedApplication.AccountLVM.SelectedAccount}"
it is creating a new AccountLVM, which does not have the SelectedAccount property set.
You don't see the existing DataGrid.SelectedItem change at all because it's still bound to the old AccountLVM as no PropertyChange notification got raised when _accountLVM changed, so the binding doesn't know to update.
But some other miscellaneous related to your code:
Don't change the private version of the property unless you also raise the PropertyChange notification for the public version of the property. This applies to both your constructors and your GetXxxxx() methods like GetAccounts().
Don't return a method call from your getter. Instead set the value using your method call if it's null, and return the private property afterwards.
public AccountListViewModel AccountLVM
{
get
{
if (_accountLVM == null)
GetAccounts(); // or _accountLVM = GetAccountLVM();
return _accountLVM;
}
set { ... }
}
It's really confusing to have the DataContext set in so many controls. The DataContext is the data layer behind your UI, and it's easiest if your UI simply reflects the data layer, and having to go all over the place to get your data makes the data layer really hard to follow.
If you must make a binding to something other than the current data context, try to use other binding properties to specify a different binding Source before immediately going to change the DataContext. Here's an example using the ElementName property to set the binding source:
<TextBox x:Name="txtTitle" ...
Text="{Binding ElementName=dtgAccounts, Path=SelectedItem.Title}" />
The DataContext in inherited, so you don't ever need to write DataContext="{Binding }"
You may want to consider re-writing your parent ViewModel so you can setup XAML like this, without all the extra DataContext bindings or 3-part nested properties.
<ComboBox ItemsSource="{Binding ApplicationList}"
SelectedItem="{Binding SelectedApplication}" />
<DataGrid ItemsSource="{Binding SelectedApplication.Accounts}"
SelectedItem="{Binding SelectedAccount}" />
<StackPanel DataContext="{Binding SelectedAccount}">
...
</StackPanel>
If you're new to the DataContext or struggling to understand it, I'd recommend reading this article on my blog to get a better understanding of what it is and how it works.

Well one major problem with this Binding method is, that the value is only updated, when the last property value, in your case SelectedAccount, is changed. The other levels are not watched by the BindingExpression, so if e.g. SelectedApplication.AccountLVM is changed the DataContext will not notice a difference in SelectedAccount because the binding is still 'watching' on the old reference and you're modifying another reference in your VM.
So I think at the start of the application SelectedApplication is null and the Binding of the ComboBox doesn't notice that it changes. Hmm, I thought about another binding solution, but I couldn't found one. So I suggest, that you create an additional property for reflecting SelectedAccount in your ApplicationListViewModel class.

WPF Tree doesn't work

Could you tell me why I can't see subItems?
I've got winforms apps and I added my wpfusercontrol:ObjectsAndZonesTree
ServiceProvider is my webservice. Adn method to get listofcountires with subitems works properly (i get countires, regions from this countires, provinces etc...)
ElementHost elementHost = new ElementHost
{
Width = 150,
Height = 50,
Dock = DockStyle.Fill,
Child = new ObjectsAndZonesTree()
};
this.splitContainer3.Panel1.Controls.Add(elementHost);
XAML:
<TreeView Name="GroupView" Grid.Row="0" Grid.Column="0" ItemsSource="{Binding}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Country
}" ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:Region}" >
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:Province}" >
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
</TreeView.Resources>
</TreeView>
XAML.CS
public ObjectsAndZonesTree()
{
InitializeComponent();
LoadView();
}
private void LoadView()
{
GroupView.ItemsSource = new ServiceProvider().GetListOfObjectsAndZones();
}
class Country:
public class Country
{
string _name;
[XmlAttribute]
public string Name
{
get { return _name; }
set { _name = value; }
}
string _code;
[XmlAttribute]
public string Code
{
get { return _code; }
set { _code = value; }
}
string _continentCode;
[XmlAttribute]
public string ContinentCode
{
get { return _continentCode; }
set { _continentCode = value; }
}
public Region[] ListOfRegions
{
get { return _listOfRegions; }
set { _listOfRegions = value; }
}
private Region[] _listOfRegions;
public IList<object> Items
{
get
{
IList<object> childNodes = new List<object>();
foreach (var group in this.ListOfRegions)
childNodes.Add(group);
return childNodes;
}
}
}
Class Region:
public class Region
{
private Province[] _listOfProvinces;
private string _name;
private string _code;
public Province[] ListOfProvinces
{
get { return _listOfProvinces; }
set { _listOfProvinces = value; }
}
public string Name
{
get {
return _name;
}
set {
_name = value;
}
}
public string Code
{
get {
return _code;
}
set {
_code = value;
}
}
public string CountryCode
{
get { return _countryCode; }
set { _countryCode = value; }
}
private string _countryCode;
public IList<object> Items
{
get
{
IList<object> childNodes = new List<object>();
foreach (var group in this.ListOfProvinces)
childNodes.Add(group);
return childNodes;
}
}
}
It displays me only list of countires.

Your Region DataTemplate needs to be a HierarchicalDataTemplate to support nested items (SubItems). You also need to specify it's ItemsSource.
<TreeView Name="GroupView" Grid.Row="0" Grid.Column="0" ItemsSource="{Binding}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Country}"
ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Region}"
ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:Province}">
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
</TreeView.Resources>
</TreeView>
So for example if you add Cities to your Provinces the changes in your XAML might look something like this.
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Province}"
ItemsSource="{Binding Cities}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:City}">
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>

Not sure where your problem is, but I thought I would share you the best resource I've found when dealing with Treeview. Thoses extension methods saved me a lot of hassle :
http://www.scip.be/index.php?Page=ArticlesNET23
They transform any flat list into a Ienumerable of HierarchyNode using some nice lambda syntax. It is implemented with IQueryable, which means efficient even against a linq datacontext.

Have you implemented INotifyPropertyChanged on Binding source class??
Plus you can check for binding exceptions in output window of visual studio.
It will help you understanding invalid bindings.

You'll need HierarchialDataTemplates instead of plain DataTemplates.
The others wrote everything, so I'll post some useful links:
http://www.codeproject.com/KB/WPF/TreeViewWithViewModel.aspx
http://blogs.msdn.com/mikehillberg/archive/2006/10/11/a-treeview-a-hierarchicaldatatemplate-and-a-2d-collection-walk-into-a-bar.aspx
http://msdn.microsoft.com/en-us/library/system.windows.hierarchicaldatatemplate.aspx