Let's say I have a ContentControl with a ContentTemplateSelector. If the Content doesn't map to a template in the DataTemplateSelector, it seems that the ContentControl defaults to displaying the Content's type as a string in a TextBlock. I want to collapse the ContentControl in this default case. Is that possible?
If the Content doesn't map to a template in the DataTemplateSelector
This shouldn't happen.
Does your ContentTemplateSelector return null in some cases?
Returning null is effectively the same as returning <TextBlock Text="{Binding}"/>.
Instead of null, return an empty template
private statiŃ readonly DataTemplate Empty = new DataTemplate();
------------
{
-----------
return Empty;
}
The responsibility of a ContentTemplateSelector is to select a template based on the Content.
If you want to hide the entire ControlControl, you could use a Style with a DataTrigger that binds to the same property that you use to select a template in the ContentTemplateSelector:
<ContentControl>
<ContentControl.Style>
<Style TargetType="ContentControl">
<Style.Triggers>
<DataTrigger Binding="{Binding YourProperty}" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed" />
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
Note that the logic that decides whether to hide the control doesn't belong to the selector.
Related
I have an ObservableCollection of custom objects bound via a DataContext to a ListBox.
Next to the ListBox a have a group of TextBox that are bound to the current item's field. (i.e. Text={Binding Path=/SomeField})
How can I disable / grey out the record detail TextBoxes when my DataContext's ObservableCollection is empty?
You could do it with a style:
<Style TargetType="TextBox">
<Style.Triggers>
<!-- When the collection itself is null -->
<DataTrigger Binding="{Binding }" Value="{x:Null}">
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
<!-- When the collection has no items -->
<DataTrigger Binding="{Binding Count}" Value="0">
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
</Style.Triggers>
</Style>
This answer assumes that you are using mvvm and have a viewmodel to back up your view - I would create a readonly bool property in your viewmodel and return true if the count of your observable collection > 0.
You can then bind the bool to the isEnabled property of the necessary text boxes, thus enabling or disabling them depending upon the value(s) of your observable collection.
EDIT - As per BenjaminPaul's comment below, the change event must be handled for your observable collection and you should then call propertyChanged on your bool property to ensure is is updated and passed back to the view.
Hello WPF aficionados,
I have a content control inside a user control that sets it data context to the selected item of a listview inside the same usercontrol. The selected item property on the view model is called Selection.
Here is the content control's declaration:
<ContentControl DataContext="{Binding Selection}">
<ContentControl.Style>
<Style TargetType="ContentControl">
<Setter Property="Template" Value="{StaticResource JobSnapShotProgDetail}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding bTandM}" Value="1">
<Setter Property="Template" Value="{StaticResource JobSnapShotProgDetail}"/>
</DataTrigger>
<DataTrigger Binding="{Binding bTandM}" Value="0">
<Setter Property="Template" Value="{StaticResource JobSnapShotTM_Detail}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
The Templates are defined as ControlTemplates in another resource file like:
<ControlTemplate x:Key="JobSnapShotProgDetail" >
...
</ControlTemplate >
<ControlTemplate x:Key="JobSnapShotTM_Detail" >
...
</ControlTemplate >
The binding works great meaning that the template's fields all display the correct data from the Selection object.
My Problem:
I want the content control to use one of two different control templates based on the value of the Selection's bTandM property.
What happens now:
When I change the selection of the listview, which changes the Selection object, the template IS NOT being changed based on the value of the Selection's bTandM property (a sql server bit data type). Yes the Selection object implements iNotifyPropertyChanged, and the ControlTemplate's fields that bind to the Selection's properties all display the correct data without any binding errors in the output window.
What I Tried:
It seems like the datatrigger is not getting "HIT" by the code. I tried to break the datatrigger by adding foo instead of a number which should have not been able to convert, but no error is generated. ie:
<DataTrigger Binding="{Binding bTandM}" Value="foo">
This leads me to believe that the trigger is not firing for some reason.
Question:
Can someone help me figure out why this data trigger has no effect.
Thanks in advance
JK
EDIT 1:
I tried to use a technique found HERE, but it also does not work. THe data triggers are not getting fired.
New attempt using DataTemplate with DataTriggers that target a contentcontrol's template property:
<ItemsControl ItemsSource="{Binding SelectionCollection}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<ContentControl x:Name="DetailControl" Template="{DynamicResource JobSnapShotProgDetail}" />
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding bTandM}" Value="False">
<Setter TargetName="DetailControl" Property="Template" Value="{DynamicResource JobSnapShotProgDetail}" />
</DataTrigger>
<DataTrigger Binding="{Binding bTandM}" Value="1">
<Setter TargetName="DetailControl" Property="Template" Value="{DynamicResource JobSnapShotTM_Detail}" />
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Again, the template loads fine and the properties are display correctly for the initial template set in the style setter, but the templates do not change based on the object's bTandM boolean property.
Okay, so this turned out to be an issue with NotifyPropertyChanged.
The selection property of my viewmodel does implement INPC but the problem was that the underlying class type (vw_Job_Snapshot which is a mapped entity from a sql server view) of selection did not.
I had to implement iNPC in the underlying class and then in my viewmodel use the Property Setter for the Selection Property to also notify the specific bTandM property change like so:
Public Property Selection As vw_Job_Snapshot
Get
Return Me._Selection
End Get
Set(ByVal value As vw_Job_Snapshot)
Me._Selection = value
''Notify of specific property changed
value.OnPropertyChanged("bTandM")
_Selection = value
RaisePropertyChanged(JobSnapshotSelectedPropertyName)
End Set
End Property
After this the following code in my view worked perfectly:
<ContentControl DataContext="{Binding Selection}">
<ContentControl.Style>
<Style TargetType="ContentControl">
<Setter Property="Template" Value="{DynamicResource JobSnapShotTM_Detail}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding bTandM}" Value="False">
<Setter Property="Template" Value="{DynamicResource JobSnapShotProgDetail}"/>
</DataTrigger>
<DataTrigger Binding="{Binding bTandM}" Value="True">
<Setter Property="Template" Value="{DynamicResource JobSnapShotTM_Detail}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
Thanks to everyone who helped
Try using a DataTemplateSelector instead.
Your selector would look something like this (I'm assuming your class is called JobSnapShot):
public class JobSnapShotDataTemplateSelector : DataTemplateSelector
{
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
FrameworkElement element = container as FrameworkElement;
if (element != null && item != null && item is JobSnapShot)
{
JobSnapShot jobSnapShot = item as JobSnapShot;
if (jobSnapShot.bTandM == 1)
return
element.FindResource("JobSnapShotProgDetail") as DataTemplate;
else
return
element.FindResource("JobSnapShotTM_Detail") as DataTemplate;
}
return null;
}
}
XAML:
<Window.Resources>
<local:JobSnapShotDataTemplateSelector x:Key="myDataTemplateSelector"/>
</Window.Resources>
<ContentControl ItemTemplateSelector="{StaticResource myDataTemplateSelector}" .... />
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>
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.