Hello WPF Pros at least I hope some of you read this!
DataContext is a property on FrameworkElement (base class for all WPF Controls) and is implemented as a DependencyProperty. That means all the descendant elements in the logical tree share the same DataContext.
So the ContentControl should do it with its descendant elements right?
I have a scenario where that is NOT the case and I would like to know WHAT is the cause of that misbehaviour ?!
That you understand a bit more about it please read this thread ( dont NOT want to copy everything here) where the trouble starts...:
WPF: Can not find the Trigger target 'cc'. The target must appear before any Setters, Triggers
and to say it in short words: My DataTemplates within the ContentControl do have a dead DataContext that means there is NOTHING to bind to it, what is actually not possible...
Every Element down the ContentControl has NOTHING set in the DataContext Property ???
DataContext is a property on
FrameworkElement (base class for all
WPF Controls) and is implemented as a
DependencyProperty. That means all the
descendant elements in the logical
tree share the same DataContext.
The fact that it's a dependency property doesn't imply inheritance... It's true for DataContext, but only because the dependency property has the FrameworkPropertyMetadataOptions.Inherits flag in its metadata.
So the ContentControl should do it
with its descendant elements right?
ContentControl is a bit special: the DataContext of its descendants (the visual tree built from the DataTemplate) is actually be the Content of the ContentControl. So if your ContentControl has no content, the DataContext inside it is null.
This worked for me:
<ContentControl ContentTemplate="{StaticResource NotesTemplate}"
Content="{Binding}"
DataContext="{Binding HeightField}"/>
Without the Content="{Binding}", the DataContext was NULL
The last answer (from VinceF) worked for me too.
I wanted to show a usercontrol depending on the value of a property in my viewmodel. So I made a ContentControl with some Style Triggers. Depending on the value of a bind property the trigger sets a specific ContentTemplate containing the specific usercontrol.
The usercontrol was shown right, but its DataContext was always null. So I had to set the Context of the ContentControl to: Content="{Binding}" After that, the UserControls worked fine and had the same DataContext as their parent.
So my XAML looks like that:
In the Resources part I defined two DataTemplates; each one for each UserControl I want to show.
<DataTemplate x:Key="ViewA">
<namespace:UserControlA/>
</DataTemplate>
<DataTemplate x:Key="ViewB">
<namespace:UserControlB/>
</DataTemplate>
The part where I show the UserControl depending on a property is the following:
<ContentControl Content="{Binding}">
<ContentControl.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Property}" Value="0">
<Setter Property="ContentControl.ContentTemplate" Value="{StaticResource ViewA}" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=Property}" Value="1">
<Setter Property="ContentControl.ContentTemplate" Value="{StaticResource ViewB}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
after reading this question and previous answers, I prefer using ContentControl with data triggered Content like this:
Controls which will be set as Content of ContentControl:
<TextBox x:Key="ViewA">
...
</TextBox>
<ComboBox x:Key="ViewB">
...
</ComboBox>
ContentControl which switch own content by DataTrigger in ContentControl style:
<ContentControl>
<ContentControl.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Property}" Value="0">
<Setter Property="Content" Value="{StaticResource ViewA}" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=Property}" Value="1">
<Setter Property="Content" Value="{StaticResource ViewB}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
I hope this helps to someone like previous answers to me.
Related
Okay, I have a relatively involved problem. I'm trying to create a Window in WPF. The main element on this window is a DataGrid. Each one of the rows in the DataGrid has a DetailsPane which I set using DataGrid.RowDetailsTemplate. Depending on certain row-specific values, I need the DetailsPane to display different elements. To accomplish this I placed a ContentControl at the root of the DataTemplate and used a Style with DataTriggers to set its Content property. Now, inside one of these Setters is a ComboBox. This ComboBox needs to have its ItemsSource bound to a list, which is stored in a dependency property on the Window level (because its the same list regardless of the row). Below is a simplified version of what I'm looking at:
<Window>
...
<DataGrid>
...
<DataGrid.RowDetailsTemplate>
<DataTemplate>
<ContentControl>
<Style TargetType="ContentControl">
<Style.Triggers>
<DataTrigger Binding="{Binding RowSpecificBooleanProperty}" Value="False">
<Setter Property="Content">
<Setter.Value>
...
<ComboBox ItemsSource={HowDoIBindThisToTheWindowProperty}/>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl>
</DataTemplate>
</DataGrid.RowDetailsTemplate>
</DataGrid>
</Window>
So what I'm trying to figure out is how to bind the ItemsSource of that ComboBox to a dependency property of the top-level window. Andy idea how to accomplish that?
EDIT:
I should have mentioned this before but I've already tried using {RelativeSource AncestorType=Window} and ElementName in the binding. In both cases the list in the ComboBox is blank at runtime.
ItemsSource="{Binding WhateverList, RelativeSource={RelativeSource AncestorType=Window}}"
I try to access a ToggleButton that is within a separate UserControl to Trigger a DockPanel.Style DataTrigger.
Here is how I made it work when both, the ToggleButton and the DockPanel, are in the same namespace:
<ToggleButton x:Name="OneToggleButton"
Content="Click me..." />
<DockPanel>
<DockPanel.Style>
<Style>
<Setter Property="UIElement.Visibility"
Value="Visible"/>
<Style.Triggers>
<DataTrigger Binding="{Binding IsChecked,
ElementName=DetailsBookToggleButton}"
Value="False">
<Setter Property="UIElement.Visibility"
Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</DockPanel.Style>
<TextBlock DockPanel.Dock="Top" Text="..." />
</DockPanel>
But now when I move the ToggleButton into an other file (other namespace) it doesn't work anymore. ElementName (as I understand it) only works for elements within the same file.
So how can I manage a Binding to the IsChecked of my ToggleButton in another file?
Anybody have a suggestion? Would be great :)
FYI, the term you are looking for is "name scope", and there is no way to reference an element defined in another name scope. Arguably, you should not be allowed to do this.
Rather than binding one UI element to another, consider binding them both to a common property, either in your view model, on some common ancestor element, or via dependency property inheritance.
I have a View/ViewModel pair properly working with Caliburn.Micro.
Inside the view, there is a ContentControl whose content is bound to the same viewmodel, and depending on the value of a given enumerated property in the viewmodel, I want a different template for the ContentControl:
<ContentControl Content="{Binding}">
<ContentControl.Resources>
<DataTemplate x:Key="TurnedOffView">
<local:TurnedOffView/>
</DataTemplate>
<DataTemplate x:Key="DeviceReadyView">
<local:DeviceReadyView/>
</DataTemplate>
</ContentControl.Resources>
<ContentControl.Style>
<Style TargetType="ContentControl">
<Setter Property="ContentTemplate" Value="{StaticResource TurnedOffView}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding State}" Value="{x:Static local:DeviceStates.Ready}">
<Setter Property="ContentTemplate" Value="{StaticResource DeviceReadyView}"/>
</DataTrigger>
<!-- More DataTriggers here, one for each state -->
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
I know Caliburn.Micro can use cal:View.Model and cal:View.Context so that multiple views can be bound to each ViewModel, but I can't figure out how to use this to avoid all this verbosity.
So the question is:
How should I use View.Model and View.Context (and rename my views) in this scenario to take advantage of Caliburn.Micro convention-over-configuration approach?
<ContentControl cm:View.Model="{Binding}" cm:View.Context="{Binding ContextProp, Mode=TwoWay}" /> might be something to try... Then your context would be based off code in your viewmodel not having to structure datatemplates with view-first code. ContextProp would be basically a sub view of your view in question (based on namespace Project.Views.MainView.Main.TurnedOff) ContextProp = "TurnedOff";
yea sorry.. Its how I see the folder structure (namespaces)... So instead of TurnedOffView it could be TurnedOff.xaml under a folder named Main. This was assuming your primary view is MainView.xaml and your primary Viewmodel is MainViewModel.cs. SOrry for the confusion.
View.Model can be setup to do multiple viewmodels, at that rate you might want to think about Conductor in the framework. But I don't think it would be warranted since you are basically doing view switching in the presented case above.
I have a ContentControl that I need to set it's ContentTemplate dynamically.
so I decided to write 2 DataTemplates, and then style my ContentControl such that a trigger fires and set the proper template (dt1/dt2) when a Boolean dependency property in my view-model changes (true/false).
But the problem is if the Boolean property is primarily set to true, the data template will always be dt1 and changing the property to false wont change the template to dt2.
since the data triggers are bound to the Boolean dependency property, shouldn't changing the property result in firing the triggers?
notes:
There is a button in MyView which changes BooleanDependencyProp on it's
click event.
MyViewModel inherits from an interface that
implements INotifyPropertyChanged.
Xaml:
<UserControl x:Class="Views.MyView">
...
<StackPanel>
<ContentControl Content="{Binding RelativeSource={RelativeSource AncestorType=MyView}, Path=MyViewModel}">
<ContentControl.Style>
<Style TargetType="{x:Type ContentControl}">
<Style.Triggers>
<DataTrigger Binding="{Binding BooleanDependencyProp}" Value="true">
<Setter Property="ContentTemplate">
<Setter.Value>
<dt1 ... />
</Setter.Value>
</Setter>
<DataTrigger Binding="{Binding BooleanDependencyProp}" Value="false">
<Setter Property="ContentTemplate">
<Setter.Value>
<dt2 ... />
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
</StackPanel>
This is a known shortcoming of the WPF framework, if you want to apply different data templates, consider either using the visual state manager to change the presentation, or swap out the content data template for a user control that changes based on the triggers instead, you'll get more mileage.
There's a lot more I could say, but it would involve knowing your scenario and the differences in these DataTemplates, why you are disambiguating, etc. Also, MVVM all around? or straight ahead Code+Markup style with a few view models?
I'm working on a custom class that descends from DataGridColumn. The base class for DataGridColumn is DependencyObject. As such, it does not have a Tooltip property.
I want my custom class to have a Tooltip property. Actually, I want it to also have a ToolTipTemplate property that is a DataTemplate that can be used to generate the ToolTip. How do I go about adding this functionality to my class?
Tony
Its a common misconception that DataGridColumn being a dependency object, is part of the visual tree. It is not. So even if we create an inheritable dependency property (just like DataContext or FlowDirection which automatically propagates down the visual parent to its child elements), the new property of ToolTip wont descend down to individual cells, as those cells are not the children of the data grid column.
So now that we know this, the only way left is to add a binding in the CellStyle and bind to the self Column.ToolTip property. Just because you have decided to go with ToolTipTemplate, then you could add a ContentControl and then bind to its content template.
Something like this...
<tk:DataGrid x:Name="MyDataGrid" RowHeaderWidth="15"
ItemsSource="{StaticResource MyData}"
AutoGenerateColumns="False">
<tk:DataGrid.CellStyle>
<Style TargetType="{x:Type tk:DataGridCell}">
<Setter Property="ToolTip">
<Setter.Value>
<ContentControl
ContentTemplate="{Binding Column.ToolTipTemplate,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type tk:DataGridCell}}}"/>
</Setter.Value>
</Setter>
<Style.Triggers>
<DataTrigger
Binding="{Binding Column.ToolTipTemplate,
RelativeSource={RelativeSource Self}}"
Value="{x:Null}">
<Setter Property="ToolTip" Value="{x:Null}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</tk:DataGrid.CellStyle>
....
</tk:DataGrid>