I have a problem. I made a DataTemplate for a TreeView and I need to set the initial value of the ToggleButton's IsChecked property depending on my model. But it turns out that setting this property using triggers/setters disables the databinding.
Is it so? If yes, give me a suggestion how it can be fixed?
<DataTemplate x:Key="CellTemplate_Name">
<DockPanel x:Name="dock">
<ToggleButton x:Name="Expander"
IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource AncestorType={x:Type TreeViewItem}}}"> <--- Binding
...
<ToggleButton/>
...
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=ObjIsOpened, Converter={StaticResource DebugConverter}}" Value="true"> <--- Trigger
<Setter TargetName="Expander" Property="IsChecked" Value="true"></Setter>
</DataTrigger>
...
</DataTemplate.Triggers>
</DataTemplate>
Regards, Lerax.
First of all I suggest you read the excellent article by Josh Smith
Simplifying the WPF TreeView by Using the ViewModel Pattern
Based on that article, I would suggest defining a style for the TreeViewItem (using the ItemContainerStyle property of the TreeView) which binds its IsExpanded property to your model object's ObjIsOpened property. Then get rid of your trigger.
Example:
<Style TargetType="TreeViewItem">
<Setter Property="IsExpanded"
Value="{Binding ObjIsOpened, Converter={StaticResource DebugConverter}}"/>
</Style>
<DataTemplate x:Key="CellTemplate_Name">
<DockPanel x:Name="dock">
<ToggleButton x:Name="Expander"
IsChecked="{Binding Path=IsExpanded,
RelativeSource={RelativeSource
AncestorType={x:Type TreeViewItem}}}"> <--- Binding
...
<ToggleButton/>
...
</DataTemplate>
I suspect they do not disable data binding, they just have higher priority. Instead of using binding and trigger at the same time, why don't you use one of them (either binding or trigger)? E.g. you could bind to model directly, and don't use trigger at all...
Related
Why is it that the binding Marked stops working when the triggers are used? Is there some way to fix this?
The multi selection ListBox has ListBoxItems with CheckBoxes, and the checkbox in an item is ticked when the corresponding item is selected, using mouse or keyboard or touch or whatever. The point with this demo is to not tick the checkboxes directly, but just multiselect the items and see the checkboxes get ticked as a consequence of that. This synchronization in the XAML works well, but since the Marked binding isn't working, the model won't get updated.
If I remove the triggers, then the binding Marked starts working. I know, because then the model gets updated when the checkboxes are ticked.
If I attach event handlers for Checked and Unchecked to the CheckBox, they fire even when the triggers are there.
<ListBox ItemsSource="{Binding Lines}" SelectionMode="Extended">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<CheckBox x:Name="cb"
Content="{Binding DisplayText}"
IsChecked="{Binding Marked, Mode=TwoWay}">
</CheckBox>
</StackPanel>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Value="true">
<Setter TargetName="cb" Property="IsChecked" Value="true"/>
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Value="false">
<Setter TargetName="cb" Property="IsChecked" Value="false"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
EDIT:
Although the accepted solution below is good XAML, it crashes with Elmish.WPF, which I'm using. That's another issue, and will be solved through other forums.
The DataTriggers will obviously override the Binding, since the ListBoxItem's IsSelected property is always either true or false.
Replace the DataTriggers by an ItemContainerStyle:
<ListBox ItemsSource="{Binding Lines}" SelectionMode="Extended">
<ListBox.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding DisplayText}"
IsChecked="{Binding Marked}"/>
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.ItemContainerStyle>
<Style TargetType="ListBoxItem">
<Setter Property="IsSelected" Value="{Binding Marked}"/>
</Style>
</ListBox.ItemContainerStyle>
</ListBox>
I've setup a reusable datatemplate "DataGridCheckBoxEdit" for a datagrid column. Binding to it one way works like a charm through ContentControl. Binding directly works two way correctly. However, binding two way within that DataTemplate, from a ContentControl just won't work.
Here are the snippets:
<DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<ContentControl Content="{Binding Path=IsMadeAvailable, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" ContentTemplate="{StaticResource DataGridCheckBoxEdit}" />
</DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
and the reusable template:
<DataTemplate x:Key="DataGridCheckBoxEdit">
<CheckBox Name="CheckBoxControl" IsChecked="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ContentControl}, Path=DataContext.Content, Mode=TwoWay, BindsDirectlyToSource=True, UpdateSourceTrigger=PropertyChanged}" Margin="8,4,2,2" />
<DataTemplate.Triggers>
<Trigger SourceName="CheckBoxControl" Property="IsVisible" Value="True">
<Setter TargetName="CheckBoxControl" Property="FocusManager.FocusedElement" Value="{Binding ElementName=CheckBoxControl}"/>
</Trigger>
</DataTemplate.Triggers>
</DataTemplate>
As I said, one way binding works like a charm...but getting the data back to the property doesn't.
Of course, putting it without being reusable:
<DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<CheckBox Name="GasIsAvailableCheckBox" IsChecked="{Binding Path=IsMadeAvailable, UpdateSourceTrigger=PropertyChanged}" Margin="8,4,2,2" />
<DataTemplate.Triggers>
<Trigger SourceName="GasIsAvailableCheckBox" Property="IsVisible" Value="True">
<Setter TargetName="GasIsAvailableCheckBox" Property="FocusManager.FocusedElement" Value="{Binding ElementName=GasIsAvailableCheckBox}"/>
</Trigger>
</DataTemplate.Triggers>
</DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
also works great, and works two-way.
What am I doing wrong?
Thanks!
Vladan
Your binding is just broken (see the output window of Visual Studio for the respective errors), you do not want to bind to DataContext.Content but just Content, the DataContext would be the object in that row instead of the ContentControl itself.
Change that in the binding path of the reusable template and it will work. You also set a lot of properties to values they already have by default, this would be the minimal version:
{Binding Content, RelativeSource={RelativeSource AncestorType=ContentControl}}
I would like to bind the current focus to the datacontext. My menu system has a viewmodel that contains a list of ButtonViewModels as datacontext. How would I go about having the focused button be determined by the datacontext?
There is a FocusManager.FocusedElement, but this references to a control and the idea of a ViewModel is to not depend on the implementation of the View...
I tried to place a DataTrigger in the Button Style which binds to a property called IsFocused in the ButtonViewModel and in the Setter Bind FocusManager.FocusedElement to the Button where IsFocused is set to true. This should allow you to Control the Focus directly from the ButtonViewModel
<ItemsControl ItemsSource="{Binding ButtonViewModels}">
<ItemsControl.Resources>
<Style x:Key="FocusBindingStyle" TargetType="Button">
<Style.Triggers>
<DataTrigger Binding="{Binding IsFocused}" Value="True">
<Setter Property="FocusManager.FocusedElement"
Value="{Binding RelativeSource={RelativeSource Self}}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ItemsControl.Resources>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button Content="Test" Style="{StaticResource FocusBindingStyle}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I have 2 DataTemplates (A & B). A contains an Expander and the expander's HeaderTemplate is pointed at another DataTemplate (B).
DataTemplate B is shown below:
<DataTemplate x:Key="ProjectExpanderHeader">
<Border CornerRadius="2,2,0,0"
Background="{StaticResource ItemGradient}"
HorizontalAlignment="{Binding HorizontalAlignment,
RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}},
Mode=OneWayToSource}">
<local:ItemContentsUserControl Height="30"/>
</Border>
</DataTemplate>
Is it possible to set the CornerRadius of B's Border when the IsExpanded property of A's Expander is set to true?
Thanks in advance.
You could do this by introducing a new attched property of type CornerRadius (e.g. Helper.CornerRadiusProperty) and attach it to a parent of your ExpanderHeader somewhere in DataTemplate A. You set this property based on IsExpanded using a trigger.
In your DataTemplate B you bind the CornerRadius of your Border to that property using FindAncestor:
<Border CornerRadius="{Binding local:Helper.CornerRadius,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type ContentPresenter}} ...
The above example assumes that you have set the Helper.CornerRadius property on a ContentPresenter in DataTemplate A.
I found my solution. I added the following code to DataTemplateB's Triggers. What it does is look for an ancestor expander control and applies the CornerRadius property to it.
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Expander}},Path=IsExpanded}" Value="false">
<Setter TargetName="ProjectExpanderHeader" Property="CornerRadius" Value="2,2,2,2"/>
</DataTrigger>
</DataTemplate.Triggers>
Why not using the triggers ?
<DataTemplate>
<Border CornerRadius="2,2,0,0"
Background="{StaticResource ItemGradient}"
HorizontalAlignment="{Binding HorizontalAlignment,
RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}},
Mode=OneWayToSource}">
<Border.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding DataTemplateA.IsExpanded}"
Value="True">
<Setter Property="Border.CornerRadius"
Value="2,2,0,0" />
</DataTrigger>
</Style.Triggers>
</Style>
</Border.Style>
<local:ItemContentsUserControl Height="30" />
</Border>
</DataTemplate>
I have a ViewModel that provides a collection of Items. There is also a ActiveItem propery. The Items collection may or may not contain ActiveItem.
What I want to do (in XAML) is display the items as a list and highlight any of the items that are equal to Active Item.
I have tried the following with no success:
<ListBox ItemsSource="{Binding Items}">
<ListBox.ItemTemplate>
<DataTemplate>
<Border x:Name="outerBorder" Background="Green">
<TextBlock Text="{Binding ItemId}" />
</Border>
<DataTemplate.Triggers>
<DataTrigger
Binding="{Binding
Path=DataContext.Item.ItemId,
RelativeSource={RelativeSource TemplatedParent},
Mode=Default}"
Value="{Binding
Path=DataContext.ActiveItem.ItemId,
RelativeSource={RelativeSource AncestorType=Window},
Mode=Default}"
>
<Setter TargetName="outerBorder"
Property="Background" Value="Orange" />
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
As you can see I attempted to use a DataTrigger to match the current item with the ActiveItem but it doesn't work. I think this is something to do with my trying to use a Binding in DataTrigger.Value - something I haven't seen any other examples of.
Any ideas how I might make this work?
Thanks,
Daniel
Since you're using MVVM, why not just have the view model expose a property telling the view whether it's active or not? That'll get that logic out of you view and into your VM.