How do I achieve the following:
<ComboBox
IsEnabled="{Binding bVisibilty = AnotherCollection.Count > 0 ? true:false}"/>
I can use a converter which will be converting count to boolen, but is there a better way of doing than overdoing converter everywhere.
You can use style triggers for that like so :
<ComboBox >
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<DataTrigger Binding="{Binding AnotherCollection.Count}" Value="0">
<Setter Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>
Obviously AnotherCollection needs to be an ObservableCollection so the UI will be notified every time item is being added\removed to it
You could bind to a Property on your ViewModel and put the boolean and INPC logic in the viewmodel
Related
I have a combobox which is bound to an Enum datatype. Right now the combobox binding works fine but when I tried to bind the visibility of a checkbox to the combobox selection, this binding is not working as expected. What I wanted to do was whenever the combobox selection is "Restore", I want a checkbox to be visible. Below is the code that I am using.
<CheckBox.Style>
<Style TargetType="CheckBox">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=cmbOperation, Path=SelectedValue}" Value="Restore">
<Setter Property="Visibility" Value="Visible"></Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
I tried changing the Path between SelectedValue, SelectedItem , SelectedValue.TosString() (hopelessly) but I am not getting the checkbox to change its visibility whenever the combobox has "Restore" as its selection. Should I be making any changes in the Enum that I am binding to the Combobox ? If not, what else am I doing wrong?
I'm willing to bet that you've set Visibility on the CheckBox in the XAML:
<CheckBox
Visibility="Collapsed"
>
However, due to the rules of Dependency Property Value Precedence in WPF, that will override anything that happens in the Style. This is by design and it's not a bad idea when you think through all the implications, but it bites everybody who's new to WPF.
It's an easy fix: Just set the starting value in a Setter in the Style. What the Style does, the Style can undo.
<CheckBox
>
<CheckBox.Style>
<Style TargetType="CheckBox">
<Setter Property="Visibility" Value="Collapsed" />
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=cmbOperation, Path=SelectedValue}" Value="Restore">
<Setter Property="Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
I want to have a StackPanel who's visibility should be depending on a Combobox selection. Unfortunatly the XAML below does not work.
I found a solution with a new property which will be set on the PropertyChanged event of the Combobox selection, though I would prefer a strict XAML solution for this.
Any hints on how to solve this?
<StackPanel>
<Label>Picture in Picture function</Label>
<ComboBox Name="cbPictureInPicture" ItemsSource="{Binding Path=PictureInPictureCodeList, Mode=OneWay}" DisplayMemberPath="CodeText"
SelectedValuePath="CodeID" SelectedValue="{Binding Path=PictureInPicture, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
<StackPanel>
<StackPanel.Style>
<Style TargetType="StackPanel">
<Setter Property="Visibility" Value="Visible" />
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=cbPictureInPicture, Path=IsSelected.CodeText}" Value="Yes">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
</Style.Triggers>
</Style>
</StackPanel.Style>
<Label>Picture in Picture is used</Label>
(...)
</StackPanel>
you may perhaps rewrite the same as
<DataTrigger Binding="{Binding ElementName=cbPictureInPicture, Path=SelectedItem.CodeText}" Value="Yes">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
assuming the combobox is bound to a collection whose item has CodeText property. so SelectedItem.CodeText will point to the same.
additionally it may not be required to set <Setter Property="Visibility" Value="Visible" /> as it is the default value. it does not have any effect in this case just some extra line of code which can be removed.
You can also use a converter and bind directly to the PictureInPicture property:
<StackPanel Visibility="{Binding PictureInPicture, Converter={StaticResource myVisibilityConverter}}"/>
<Label>Picture in Picture is used</Label>
(...)
</StackPanel>
Create flags and pass this flag in stackpanel visibility converter.
On the basis of flag in converter make decision stackpanel visible/hide whatever
Set this flat in comboBox selection change event if selected value as per your requirement.
I would like to make a WPF usercontrol that shows a string when and only when the datacontext == null. I'm using the TargetNullValue attribute in binding to display a custom string when the datacontext is null, and that's working as intended. But when the datacontext is non-null, it just shows the ToString value, which I would like to get rid of.
Of course I could solve this easily by using a valueconverter, but I'd like to find a way to solve this with xaml only. Does anyone know a way to do it?
In case you want TextBlock to be shown only in case binding value is null, you can have trigger in place and set Visibility to Visible when binding value is null and otherwise Collapsed always.
<TextBlock Text="{Binding TargetNullValue=NullValue}">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Setter Property="Visibility" Value="Collapsed"/>
<Style.Triggers>
<DataTrigger Binding="{Binding}" Value="{x:Null}">
<Setter Property="Visibility" Value="Visible"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
Use a data trigger on {x:Null}. There are many options using styles, data templates etc., depending on taste and needs. For instance:
<DataTemplate x:Key="ShowOnNull">
<TextBlock x:Name="text"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding}" Value="{x:Null}">
<Setter TargetName="text" Property="Text" Value="your custom string"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
...
<ContentPresenter ContentTemplate="{StaticResource ShowOnNull}"
Content="{Binding ...}"/>
Can someone provide a simple example how could you use DataTriggers on an ItemsControl?
For example if i say something like this:
<ItemsControl.Triggers>
<DataTrigger Binding="{Binding Items.Count}" Value="2">
<Setter TargetName="DocHost" Property="UniformGrid.Rows" Value="2"/>
</DataTrigger>
</ItemsControl.Triggers>
It gives me an error saying that ItemsControl expects an event trigger. Sadly i must use DataTriggers inside and ItemsControl. How can i do that?
You cannot use a DataTrigger in a TriggerCollection... yes, yes, I know... it's madness. However, you can put one in the TriggerCollection of a Style:
<ItemsControl.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding Items.Count}" Value="2">
<Setter TargetName="DocHost" Property="UniformGrid.Rows" Value="2"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ItemsControl.Style>
UPDATE >>>
Sorry, I didn't see that TargetName in there. The answer is to move this DataTrigger into the UnifrmGrid.Style instead and remove the TargetName property, but then you might have some trouble Binding to the Items property... let me know if you have any more problems.
I want to change the style of the button on the basis of if else condition when first the wpf application is getting loaded. On application loaded using if, there will be one style of button and in else part, there will be another. How to achieve this using Datatriggers or else using MVVM pattern.
Kindly Suggest?
Thanks
You can use Style.Setters to set default value. For other determined conditions use Style.Triggers. This works like if else.
<TextBlock.Style>
<Style TargetType="TextBlock">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=EditorWindow, Path=Category}" Value="R">
<Setter Property="Visibility" Value="Visible"/>
</DataTrigger>
</Style.Triggers>
<Style.Setters>
<Setter Property="Visibility" Value="Collapsed"/>
</Style.Setters>
</Style>
</TextBlock.Style>
Alternatively, if you want to use DataTriggers, you can use the following:
<Button Command="{Binding SomeButtonCommand}" Content="Click Me!">
<Button.Style>
<Style TargetType="{x:Type Button}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=NormalButtonMode, Mode=OneWay}" Value="True">
<Setter Property="Content" Value="This Button is in Normal Mode" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=NormalButtonMode, Mode=OneWay}" Value="False">
<Setter Property="Content" Value="This Button is in the Other Mode" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
In this case the ViewModel must expose the boolean property NormalButtonMode. In this example I only set the Content property of the button, but you can list any number of Setters inside the DataTrigger.
You can also put this Style in a resource dictionary and just link it for each button using StaticResource. Just make sure you expose the NormalButtonMode (or whatever) property on each and every ViewModel - maybe put it in a base class.
You should look into Data Templates and a Template Selector. Here is a hastily copy pasted example from my own code, it's not immediately applicable to buttons but I think it should help you along your way.
The following is from the application resources xaml file. I use it to decide which view to use for the ProjectViewModel based on a variable in the ViewModel:
<DataTemplate DataType="{x:Type viewmod:ProjectViewModel}">
<DataTemplate.Resources>
<DataTemplate x:Key="ProjectEditViewTemplate">
<view:ProjectEditView/>
</DataTemplate>
<DataTemplate x:Key="ServiceSelectionViewTemplate">
<view:ServiceSelectionView/>
</DataTemplate>
</DataTemplate.Resources>
<ContentControl Content="{Binding}" ContentTemplateSelector="{StaticResource ProjectViewModelTemplateSelector}" />
</DataTemplate>
The ProjectViewModelTemplateSelector is defined as follows:
public class ProjectViewModelTemplateSelector : DataTemplateSelector
{
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
FrameworkElement element = container as FrameworkElement;
if (element != null && item != null && item is ViewModel.ProjectViewModel)
{
if ((item as ViewModel.ProjectViewModel).EditMode)
{
return element.FindResource("ProjectEditViewTemplate") as DataTemplate;
}
else
{
return element.FindResource("ServiceSelectionViewTemplate") as DataTemplate;
}
}
else
return base.SelectTemplate(item, container);
}
}
}