The datatrigger below is not working. Any idea why not?
I checked in code behind that the LineCount in two situations is 1 respectively 4.
But when I change the Value to "-1" the trigger is working.
So why is the LineCount always -1?
<TextBox x:Name="TextInfo" TextWrapping="Wrap" Text="Information" HorizontalAlignment="Stretch" Foreground="OrangeRed">
<TextBox.Style>
<Style TargetType="{x:Type TextBox}">
<Style.Triggers>
<DataTrigger Binding="{Binding LineCount, ElementName=TextInfo}" Value="4">
<Setter Property="Background" Value="Green" />
</DataTrigger>
<DataTrigger Binding="{Binding LineCount, ElementName=TextInfo}" Value="1">
<Setter Property="Background" Value="PowderBlue" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
Looking at the TextBox.LineCount Property page on MSDN, we can see that it is not a DependencyProperty. Furthermore, as the TextBox class does not implement the INotifyPropertyChanged interface, I can only imagine that the value of this property will never update for you in a Binding and can only be used in code.
The only way that I can see you using this property is if you create an Attached Property to access it and expose the updated value.
A quick decompile of the TextBox code shows that LineCount is not a DependencyProperty. So when the value is updated it will not update your trigger.
This is LineCount property from the System.Windows.Controls.TextBox class in C#. You can see here that there is not DependencyProperty backing the property.
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public int LineCount
{
get
{
if (this.RenderScope == null)
return -1;
else
return this.GetLineIndexFromCharacterIndex(this.TextContainer.SymbolCount) + 1;
}
}
The answer to this question as a decent solution for creating an attached property that will observe when the text in the TextBox is modified, and give the current line position. You can change your binding to listen for the attached property.
You dont need ElementName, use RelativeSource:
<DataTrigger Binding="{Binding LineCount, RelativeSource={RelativeSource Self}}" Value="4">
The LineCount property of a TextBox can be used to retrieve the current number of lines of text in a TextBox. If the text wraps to multiple lines, this property will reflect the visible number of wrapped lines that the user sees.
<TextBox x:Name="TextInfo" Text="Information" HorizontalAlignment="Stretch" Foreground="OrangeRed" **TextWrapping="Wrap"**>
<TextBox.Style>
....
</TextBox.Style>
</TextBox>
Related
I want to show a StackPanel based on a particular condition. In this example I've used the BorderThickness property:
<ContentControl x:Name="gridDati" VirtualizingPanel.VirtualizationMode="Recycling" VirtualizingPanel.ScrollUnit="Item" HorizontalAlignment="Stretch" HorizontalContentAlignment="Stretch">
<ContentControl.Style>
<Style TargetType="ContentControl">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Items}" Value="{x:Null}">
<Setter Property="BorderThickness" Value="0" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=Items.Count}" Value="0">
<Setter Property="BorderThickness" Value="12" />
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" x:Name="pnlLoading" Visibility="Visible">
<Label Content="">
<Label.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=BorderThickness, ElementName=gridDati, UpdateSourceTrigger=PropertyChanged}" Value="0">
<Setter Property="TextBlock.Text" Value="" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=BorderThickness, ElementName=gridDati, UpdateSourceTrigger=PropertyChanged}" Value="12">
<Setter Property="TextBlock.Text" Value="STAND BY" />
</DataTrigger>
</Style.Triggers>
</Style>
</Label.Style>
</Label>
</StackPanel>
Basically when in the code behind I apply a template on gridDati, while the item counter is still zero, the border is set correctly to 12. After that it turns to zero (item binded) and this behevior is what I want.
So, I also would like to show a StackPanel at the same condition, so I used a DataTrigger but seems that is not fired at all. How can I "link" these two condition? so show a stackpanel when I have items in the datagrid?
This is the proper way to declare the Label so you get the desired result.
<Label>
<Label.Style>
<Style TargetType="Label">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Items.Count}" Value="0">
<Setter Property="Content" Value="STAND BY"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Label.Style>
</Label>
But there are a few points I need to explain to make sure you understand what I changed and why. I'm going to go through the XAML from the inside out.
First, I changed the Setter to use the right property name. You're using a Label, and your old Setter had Property="TextBlock.Text". TextBlock.Text is not a valid property name for a Label (no such property exists), so that wasn't going to work. The property you want is called Content.
Moving up one level to the DataTrigger. Instead of binding to gridDati that is binding to Items, I just bound directly to Items. You could do it the other way, but in my opinion it would be unusual and it might cause unforeseen bugs.
Next, you'll notice I removed the first DataTrigger. WPF dependency properties can be set in a number of different ways, and there is an order of precedence for which value will be taken over others. The default value (lowest precedence) for a Label's content is for it to be empty. When the DataTrigger applies the Setter, it overrides that value (it has higher precedence). When the DataTrigger condition is no longer fulfilled (Items.Count != 0), WPF stops applying the Setter and the value reverts back to the default, because there is no longer any value of higher precedence overriding it. So you don't need to add a second DataTrigger resetting to default, wit ill do that automatically.
Moving up further you'll see I changed the opening Style tag to <Style TargetType="Label">. It's common practice to set the TargetType of a Style. Doing this also gives you IntelliSense options for Setters in that Style, which might have helpped you catch the mistake you made by trying to use TextBlock.Text as a property name.
Finally, I removed Content="" from the opening Label tag. Setting the value of a property directly on an element in XAML has a very high precedence, which overrides all Styles and DataTriggers. As long as this was there, nothing you did in any Style would change anything for the Label's Content.
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 am new to WPF and I want to clear a textBox's value if a check box is unchecked. I tried doing that through data triggers.
Below is the code:
<TextBox Text="{Binding Path=Amount,Mode=TwoWay}">
<TextBox.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsSelected}" Value="false">
<Setter Property="TextBox.Text" Value="{x:Null}"></Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
My checkbox's value is set in "IsSelected" property of My Model. Here, if the checkbox is unchecked, then the text's updated value, which is {x:Null} in this case, is not reflecting in "Amount" property of my Model. Because of this the text never seems to be changed on the UI. The "Amount" earlier set value is getting set again in the TextBox because of binding
Any help is appreciated. Let me know in case you need any more information or clarification
Thanks.
In such cases I normally prefer ViewModel / Model doing the "clear" part of the functionality,
hence in your case I'd normally do something like:
public bool IsSelected {
get {
return _isSelected;
}
private set {
if (value == _isSelected)
return;
RaisePropertyChanging(() => IsSelected);
_isSelected = value;
RaisePropertyChanged(() => IsSelected);
if (_isSelected == false)
Amount = string.Empty
}
}
That way the View does not hold responsibility for any logic and thus doesn't need the DataTrigger at all
Update:
The Problem with your code is when you set the Text with a Binding in the TextBox it takes precedence over the value you set in the Style for the Text property. You can check this by using this:
<TextBox>
<TextBox.Style>
<Style TargetType="{x:Type TextBox}">
<Setter Property="Text"
Value="{Binding Path=Amount,
Mode=TwoWay}" />
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsSelected}"
Value="false">
<Setter Property="Text"
Value="{x:Null}" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
This will now clear the Text when the CheckBox is checked, however it will not be updating your Binding(Amount) since essentially your Binding is only active when the CheckBox is selected.
In a WPF application, I have correctly bound a DataTemplate to an XML node that looks like:
<answer answer="Tree", correct="false" score="10" />
In my application, I have a TextBlock with the answer in it. At first, I want it invisible, but when the correct attribute in the XML file changes to "true", it must become visible.
My DataTemplate is hooked up correctly, because everything else works. For example, if I change the answer attribute in the XML file (just for testing), it changes in my WPF view. But I'm having troubles with the visibility. This is my XAML:
<TextBlock Text="{Binding XPath=#answer}" Visibility="Hidden">
<TextBlock.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding XPath=#correct}" Value="true">
<Setter Property="TextBlock.Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
I'm guessing the Databinding in the DataTrigger isn't working correctly. Anyone have a clue?
I have run into the same problem with databound ToggleButtons. Try removing the Visibility="False" and replacing it with another DataTrigger that handles the incorrect case.
I think the issue is that the Visibility property is hard-coded. Try setting the Visibility in the style:
<TextBlock Text="{Binding XPath=#answer}">
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Visibility" Value="Hidden"/>
<Style.Triggers>
<DataTrigger Binding="{Binding XPath=#correct}" Value="true">
<Setter Property="TextBlock.Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
Sure, it works if you give a specific else case instead of just false. As in my case, it was {x:Null} and value. So when its value to bind is present, it will be true and TextBlock.Visibilty will be set using setters value and when binding path does not have any value inside it, i.e. null in my case, its simply {x:Null} :)
There is a relatively simple thing I'm trying to achieve but I'm unsure how to do it. Basically, I have a CLR class as follows:
class SomeClass
{
public SomeEnum Status;
}
public enum SomeEnum { One, Two, Three };
I've got a DataGrid that I'm binding an ObservableCollection<SomeClass> programmatically through the code-behind. In this DataGrid I have a DataGridTemplateColumn containing two buttons, as follows:
<toolkit:DataGridTemplateColumn Header="Actions">
<toolkit:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Button Content="ActionOne" />
<Button Content="ActionTwo" />
</StackPanel>
</DataTemplate>
</toolkit:DataGridTemplateColumn.CellTemplate>
</toolkit:DataGridTemplateColumn>
What I want to do is bind the IsEnabled property of these buttons to a comparison based on the value of {Binding Path=Status}. For example, in pseudocode:
ActionOne.IsEnabled = BoundValue.Status != SomeEnum.Two
ActionTwo.IsEnabled = BoundValue.Status == SomeEnum.One || BoundValue.Status == SomeEnum.Two
Is there anyway to do this in XAML? The alternative would be just to write a value converter for each button, but since the content and other details of the button may vary, too, I don't want to end up writing like 6 value converters.
Cheers!
Why not expose additional Properties in SomeClass that performs the comparison logic?
ex:
public bool ActionOneEnabled
{
get { return Status != SomeEnum.Two; }
}
Then you can easily bind the Button's IsEnabled to the appropriate Property.
Don't forget to include an OnPropertyChanged("ActionOneEnabled") in your setter for Status - so that when your Status changes your Properties based on Status are re-evaluated.
You could do this using a DataTrigger in conjunction with a Converter like below. However, Bryan's solution has the benefit of not using multiple converters and it looks like that was one of your concerns so his answer might be better for your scenario.
<Button>
....
<Button.Style>
<Style TargetType="{x:Type Button}">
<Setter Property="IsEnabled" Value="False" />
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Status, Converter={StaticResource yourConverter}}" Value="True">
<Setter Property="IsEnabled" Value="True" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
Another option would be to not use the DataTrigger and add the binding directly in the IsEnabled property:
<Button
IsEnabled="{Binding Path=Status, Converter={StaticResource yourConverter}}"
...
/>