I've copied code from the blank panorama project and made some adjustments, but somewhere something ain't right.
I've got my textblock set up:
<TextBlock Grid.Column="0" Grid.Row="0" Text="{Binding ElementName=CurrentPlaceNow, Path=Temperature}" />
My model looks like this:
public class CurrentPlaceNowModel : INotifyPropertyChanged
{
#region PropertyChanged()
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
private string _temperature;
public string Temperature
{
get
{
return _temperature;
}
set
{
if (value != _temperature)
{
_temperature = value;
NotifyPropertyChanged("Temperature");
}
}
}
}
And defined defined in the MainViewModel():
public CurrentPlaceNowModel CurrentPlaceNow = new CurrentPlaceNowModel();
Finally I've added a modifier to a buttonclick:
App.ViewModel.CurrentPlaceNow.Temperature = "foo";
Now, why isn't anything showing up in the textbox?
Your Binding should navigate through the ViewModel. Binding to an ElementName tries to look at another object in the Visual Tree.
Change your Binding to this:
<TextBlock
Grid.Column="0"
Grid.Row="0"
Text="{Binding CurrentPlaceNow.Temperature}" />
Verify your ViewModel's property is formatted properly:
private CurrentPlaceNowModel _CurrentPlaceNow = new CurrentPlaceNowModel();
public CurrentPlaceNowModel CurrentPlaceNow
{
get { return _CurrentPlaceNow; }
set
{
_CurrentPlaceNow = value;
NotifyPropertyChanged("CurrentPlaceNow");
}
}
As long as your View's DataContext is your MainViewModel, you are good to go.
You are using ElementName wrong. ElementName is when you want to bind to another XAML control, not to (view)model.
To bind to model, set instance of that model to DataContext property and bind only Path.
Related
I know this has been asked for many times. I read a lot of them and tried different ways but still could not get it to work.
The xaml code is a UserControl:
<Grid Name="middle">
<d:TextBlock Text="{x:Bind LayerNodeData.CleanName, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" Foreground="WhiteSmoke" FontSize="12" FontFamily="Arial" VerticalAlignment="Center" RelativePanel.RightOf="visibleUI" DoubleTapped="OnEditNameBegin" />
</Grid>
I set both this.DataContext and the Grid's DataContext to the data instance.
c#
public ucLayerRow(ImageLayerNode data)
{
LayerNodeData = data;
DataContext = LayerNodeData;
this.InitializeComponent();
middle.DataContext = LayerNodeData;
LayerNodeData.NotifyPropertyChanged("CleanName"); // test if it work
RefreshUI();
}
Model class
public partial class ImageLayerNode : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
// PropertyChanged is always null.
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
public string mCleanName = string.Empty;
public string CleanName {
get => mCleanName;
set { mCleanName = value; NotifyPropertyChanged();}
}
....
}
I tried add a breakpoint to the PropertyChanged and found that it is always null and thus never get called. I also tried changing the mode to OneWay, TwoWays but still nothing.
The textblock is away empty not even getting a value once.
The user control is added like this to the main page. Not sure if it is related.
var rowUI = new ucLayerRow(layerNode);
layerContainer.Children.Add(rowUI);
My UserControl's TextBlock binding doesn't update even once
During the testing, the problem looks that you use design time for usercontrol. <d:TextBlock/> please remove d: and make your usercontrol like the following.
Xaml
<Grid>
<TextBlock
VerticalAlignment="Center"
FontFamily="Arial"
FontSize="12"
Foreground="Red"
Text="{x:Bind LayerNodeData.CleanName, Mode=OneWay}" />
</Grid>
Code behind
public sealed partial class ucLayerRow : UserControl
{
public ucLayerRow(ImageLayerNode data)
{
this.InitializeComponent();
LayerNodeData = data;
}
public ImageLayerNode LayerNodeData { get; set; }
}
public partial class ImageLayerNode : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
// PropertyChanged is always null.
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
private string mCleanName = string.Empty;
public string CleanName
{
get => mCleanName;
set { mCleanName = value; NotifyPropertyChanged(); }
}
}
So what I want is when SelectedModel.TechName is updated that it physically saves to the model so that as long as the application is running it will remain whatever the user enters.
I have 2 views SelectedModel.TechName is called in both views. It pulls the data from the model however when I change views the data resets.
Any Suggestion?
edit: I am trying to make the data entered persistent, I thought setting the value would do this however every time i change between views it resets the data. In fact it blinks the data then resets it.
Field from DefaultView.Xaml
<StackPanel Grid.Row="0" Grid.Column="6" Grid.ColumnSpan="1" Margin="5 5 5 0">
<TextBox Name="techName" Text="{Binding SelectedModel.TechName,Mode=TwoWay}" BorderBrush="#FF4A5780" Grid.RowSpan="2"/>
</StackPanel>
<TextBlock x:Name="TextUpdate" Grid.Column="5" HorizontalAlignment="Left" Margin="41,0,0,0"
Grid.Row="1" Text="{Binding SelectedModel.TechName}" TextWrapping="Wrap" VerticalAlignment="Center"/>
DataModel.cs Model File
namespace callFlow.Models
{
public class DataModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string techName;
public DataModel()
{
}
public string TechName
{
get { return techName; }
set { techName = value;
OnPropertyChanged();
}
}
private void OnPropertyChanged([CallerMemberName] string techName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(techName));
}
}
}
DefaultViewModel.cs
namespace callFlow.ViewModels
{
public class DefaultViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public DefaultViewModel() { }
private ObservableCollection<DataModel> model = new ObservableCollection<DataModel>();
private DataModel selectedModel;
private DataModel _SelectedModel;
public DataModel SelectedModel
{
get { return _SelectedModel ?? (_SelectedModel = new SelectedModel()); }
set { _SelectedModel = value;
OnPropertyChanged(); }
}
public void changeSelectedModel(DataModel newSelectedModel)
{
SelectedModel.TechName = newSelectedModel.TechName;
}
private void OnPropertyChanged([CallerMemberName] string techNameVM = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(techNameVM));
}
}
}
On your binding you have
UpdateSourceTrigger=Explicit
in
Text="{Binding SelectedModel.TechName,Mode=TwoWay,
UpdateSourceTrigger=Explicit}"
When you do that, you have to write code to update the source property. Which is the viewmodel property.
Since you don't do that, the viewmodel will not get updated when you type text in there.
You should either remove that off the binding or write some more code.
There are multiple potential issues in your code. First, you use Explicit as UpdateSourceTrigger, but you never call UpdateSource, at least you do not show that in your code. Consequently, the property will never be updated. Use PropertyChanged or LostFocus instead.
If you set the UpdateSourceTrigger value to Explicit, you must call the UpdateSource method or the changes will not propagate back to the source.
Furthermore, you implement INotifyPropertyChanged in your view models, but you never call OnPropertyChanged. Hence, bindings will never be updated when a property changes its value. Your properties should look like below. This applies to all properties that you expose.
public string TechName
{
get { return techName; }
set
{
if (techName != value)
{
techName = value;
OnPropertyChanged();
}
}
}
It is not clear how you create your views and set their DataContext. If you create the data context view model in the XAML of your view, it will be created each time you instantiate a new view.
Simple solution
Remove the UpdateSourceTriger=Explicit from your DefaultView.xaml
<TextBox Name="techName" Text="{Binding SelectedModel.TechName,Mode=TwoWay}" BorderBrush="#FF4A5780" Grid.RowSpan="2"/>
Call the OnPropertyChanged method in the DataModel.TechName's setter. Like this:
public string TechName
{
get {
return techName;
}
set {
techName = value;
OnPropertyChanged();
}
}
Better solution
There are a few problems with your code. Here's how to fix them:
DefaultView.xaml
Remove the UpdateSourceTrigger=Explicit. It requires you to update the binding manually (from code) and you're not doing that.
<StackPanel Grid.Row="0" Grid.Column="6" Grid.ColumnSpan="1" Margin="5 5 5 0">
<TextBox Name="techName" Text="{Binding SelectedModel.TechName,Mode=TwoWay}" BorderBrush="#FF4A5780" Grid.RowSpan="2"/>
<TextBlock x:Name="TextUpdate" Grid.Column="5" HorizontalAlignment="Left" Margin="41,0,0,0"
Grid.Row="1" Text="{Binding SelectedModel.TechName}" TextWrapping="Wrap" VerticalAlignment="Center"/>
DataModel.cs
You were not calling the OnPropertyChanged method in TechName's setter, that's why it wasn't updating. I've done that and refactored the code a bit
public class DataModel : ObservableObject
{
private string _techName;
public string TechName
{
get => _techName;
set {
_techName = value;
OnPropertyChanged();
}
}
}
DefaultViewModel.cs
Here I've just removed the empty default constructor, the extra private DataModel field and refactored the code.
public class DefaultViewModel : ObservableObject
{
private ObservableCollection<DataModel> Models = new ObservableCollection<DataModel>();
private DataModel _selectedModel;
public DataModel SelectedModel
{
get => _selectedModel ?? (_selectedModel = new SelectedModel());
set {
_selectedModel = value;
OnPropertyChanged();
}
}
}
INotifyPropertyChanged implementation - ObservableObject.cs
I've added this class to simplify the rest of the code, since you were using the same code in both DataModel.cs and DefaultViewModel.cs
public class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
I have a TextBlock in a ComboBox in a C# WPF project bound to a list of 'Envelope' items, which have a string 'Name' and a double 'Weight' property, the former of which I would like to see displayed in the TextBlock.
When I run my program, the ComboBox appears without any text in it. It properly has three unlabeled items in it, and if I view the ItemsSource or SelectedItem of the ComboBox they show the appropriate values, and other code which interacts with the SelectedItem of the ComboBox behaves properly. The only thing that does not work is that the TextBlock contains no text. If I replace the "{Binding Name}" with "au ghdfjlnvgmumar" then the appropriate garbled characters appear in the ComboBox, so it is definitely a problem with the binding. What is the problem, and how can I get around it?
Relevant code:
xaml:
<ComboBox Name="EnvelopeList" HorizontalAlignment="Center" Width="200" >
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Name}" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
C#:
//main window code
public MainWindow()
{
InitializeComponent();
envelopes = new List<Envelope>();
envelopes.Add(new Envelope("TEST", 0));
envelopes.Add(new Envelope("HI", 10));
EnvelopeList.ItemsSource = envelopes;
}
//Envelope class
class Envelope
{
public string Name;
public double Weight;
public Envelope()
{
Name = "[None]";
Weight = 0;
}
public Envelope(string n, double w)
{
Name = n;
Weight = w;
}
public override string ToString()
{
return Name;
}
}
When DataBinding, you can only bind to Properties. Also, you need to update your properties with a PropertyChangedEvent. Otherwise, if you change your property after the initial binding it won't update the UI.
You need to use on property changed and a property
public class Envelope: ModelBase
{
private string _name;
public string Name
{
get { return _name; }
set { _name= value; OnPropertyChanged("Name"); }
}
}
public class ModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propName));
}
}
}
Finally, I notice that you're setting ItemsSource directly. Instead, you want to set your View's DataContext property and then bind to your ItemsSource
Here is a MSDN article on DataBinding that will teach you how to do it properly.
Name is a field, you can only bind to properties.
First up, is it possible to add a property to a WPF UserControl with no code behind?
If not, lets say I have a custom UserControl like this:
<UserControl x:Class="Example.Views.View"
xmlns:vm ="clr-Example.ViewModels"
xmlns:view ="clr-Example.Views"
... >
<UserControl.DataContext>
<vm:ViewModel/>
</UserControl.DataContext>
<Button Background="Transparent" Command="{Binding ClickAction}">
<Grid>
...
<Label Content="{Binding Description}"/>
</Grid>
</Button>
</UserControl>
With The ViewModel like this
public class ViewModel : INotifyPropertyChanged
{
private ICommand _clickAction;
public ICommand ClickAction
{
get { return _clickAction; }
set
{
if (_clickAction != value)
{
_clickAction = value;
RaisePropertyChanged("ClickAction");
};
}
}
private int _description;
public int Description
{
get { return _description; }
set
{
if (_description!= value)
{
_description = value;
RaisePropertyChanged("Description");
};
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
// take a copy to prevent thread issues
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
I want to be able to set the Action like this:
...
<UserControl.Resources>
<ResourceDictionary>
<command:ButtonGotClicked x:Key="gotClicked" />
</ResourceDictionary>
</UserControl.Resources>
<Grid>
<view:FuelDispenserView ClickAction="{StaticResource gotClicked}"/>
</Grid> ...
Without Code behind.
Currently I use this ugly code to achive my goal but I don't like it.
public partial class View : UserControl
{
public View()
{
InitializeComponent();
}
public ICommand ClickAction {
get {
return ((ViewModel)(this.DataContext)).ClickAction;
}
set {
((ViewModel)(this.DataContext)).ClickAction = value;
}
}
}
Does anybody have a better Idea how to do this?
P.S. This is not just meant for this Action. I have different Properties I need to add.
You can use attached properties logic to add custom properties to your user control, but It looks like you have to define different behavior for ClickAction in different views, so I'm not sure it would be useful for you. I suggest you to use routed command and command bindings - it may be helpful in this case.
I am trying to bind a ViewModel property of type Visibility to the visibility property on a Dock Panel:
Updated ViewModel Code:
public class SelectWaferButtonViewModel : INotifyPropertyChanged
{
private bool isClicked;
public SelectWaferButtonViewModel()
{
isClicked = false;
}
public bool IsControlVisible
{
get
{
return isClicked;
}
set
{
isClicked = value;
OnPropertyChanged("IsControlVisible");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnButtonClick()
{
if (isClicked)
{
IsControlVisible = false;
}
else
{
IsControlVisible = true;
}
}
protected virtual void OnPropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
and here is my updated XAML code:
<DockPanel
Name="tvwDockPanel"
Width="200"
Visibility="{Binding IsControlVisible, FallbackValue=Collapsed, Converter={StaticResource BoolToVisConverter}}"
DockPanel.Dock="Left">
<DockPanel
DockPanel.Dock="Top"
Height="22">
</DockPanel>
and I set the data context in the code behind with this line:
tvwDockPanel.DataContext = btnSelectWaferViewModel;
where btnSelectWaferViewModel is the ViewModel object for this situation.
and for fun, here is my code behind:
public partial class WaferTrackerWindow : Window
{
List<ISubscribeEvents> subscriptionList;
SelectWaferButtonViewModel btnSelectWaferViewModel;
public WaferTrackerWindow()
{
InitializeComponent();
this.InstantiateObjects();
this.SubscribeEvents();
this.SetDataContexts();
}
#region Methods
private void SetDataContexts()
{
tvwDockPanel.DataContext = btnSelectWaferViewModel.IsControlVisible;
}
private void SubscribeEvents()
{
foreach (ISubscribeEvents subscriber in subscriptionList)
{
subscriber.SubscribeEvents();
}
}
private void InstantiateObjects()
{
btnSelectWaferViewModel = new SelectWaferButtonViewModel();
subscriptionList = new List<ISubscribeEvents>();
subscriptionList.Add(
new Classes.WaferTrackerWindow.SelectWaferButtonView(btnSelectWafer, btnSelectWaferViewModel));
}
#endregion
}
All I want to do click the button btnSelectWafer and have the tvwDockPanel's visibility property to get to set to Visible via binding. Then when you click again on btnSelectWafer, tvwDockPanel's visibility property gets set back to Collapsed again. tvwDockPanel's visibility will only ever be either Collapsed or Visible.
Any help would be awesome, I am rather new to this whole data binding concept.
You have several issues here:
First of all, the intent of MVVM (if you're trying to do this with MVVM) is to separate logic from presentation. This means that in no way your ViewModel can have a reference to System.Windows.Controls.Button, nor to System.Windows.Visibility, nor to any other classes inside the System.Windows Namespace.
It is not clear to me what your SelectWaferButtonViewModel class is doing with the Button, but you need to remove the Button from there.
Also, If you need to manipulate the Visibility of a control from the ViewModel layer, you'd better use a Boolean property and the BooleanToVisibilityConverter in XAML:
ViewModel:
public bool IsControlVisible {get;set;} //Don't forget INotifyPropertyChanged!!
XAML:
<Window.Resources>
<BooleanToVisibilityConverter x:Key="BoolToVisConverter"/>
</Window.Resources>
<DockPanel Visibility="{Binding IsControlVisible, Converter={StaticResource BoolToVisConverter}}"/>
The problem is that you're binding your DockPanel to the boolean property of your view model, and then setting the Visiblity property of your UI element to the IsControlVisible property of the datacontext (which doesn't exist).
Change to:
private void SetDataContexts()
{
tvwDockPanel.DataContext = btnSelectWaferViewModel;
}