How can I show a WPF combobox with only one item differently? When there is only one item, having the possibility to select an element doesn't make sense. Therefore we would like to display only that item, instead of the combobox.
In other words, the combobox should be hidden and the first item should be displayed when there is only one item in the source collection.
You could define a Style with a DataTrigger that sets the Template property to a custom ControlTemplate when there is only a single item in the ComboBox's Items collection:
<ComboBox ItemsSource="{Binding Items}">
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<DataTrigger Binding="{Binding Items.Count, RelativeSource={RelativeSource Self}}" Value="1">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ComboBox">
<ContentControl Content="{Binding Items[0], RelativeSource={RelativeSource AncestorType=ComboBox}}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>
Related
Good afternoon,
I´m binding a list of doubles (Latlng) to an ItemsControl and in a TextBlock I want to make a custom text when the list binded has a count of 0. With the code I have the TextBlock is empty when the ItemsSource of the ItemsControl is that list.
What am I doing wrong?
Btw the list Latlng is a property of a class.
<ItemsControl Name="icLatLng" ItemsSource="{Binding Latlng}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock FontFamily="Arial" FontSize="14">
<TextBlock.Style>
<Style>
<Setter Property="TextBlock.Text" Value="{Binding}"></Setter>
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType=ItemsControl}, Path=Items.Count}" Value="0">
<Setter Property="TextBlock.Text" Value="—"></Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Thanks in advance.
Welcome to SO.
ItemsControl.ItemTemplate is the template that gets applied to each element in the Items list the control is bound to. If there are no items to begin with, then it won't be created, so anything you do in it won't be seen.
I suspect what you're really trying to do is replace the look of the entire control when the list is empty. If so, you can do that by applying a new template to the ItemsControl itself using a DataTrigger on the HasItems property:
<ItemsControl Name="icLatLng" ItemsSource="{Binding Latlng}">
<ItemsControl.Style>
<Style TargetType="{x:Type ItemsControl}" BasedOn="{StaticResource {x:Type ItemsControl}}">
<Style.Triggers>
<DataTrigger Binding="{Binding HasItems, RelativeSource={RelativeSource Self}}" Value="False">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ItemsControl}">
<TextBlock Text="-" />
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ItemsControl.Style>
</ItemsControl>
I have created a combo box in each datagrid row. The following piece of code is used to create the combo box:
<ComboBox Width="166"
ItemTemplate="{StaticResource GridBinding}"
SelectedItem="{Binding Path=Car, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, IsAsync=True}"
SelectedValue="{Binding Path=Car, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, IsAsync=True}">
<ComboBox.GroupStyle>
<GroupStyle HeaderTemplate="{StaticResource GroupHeader}" />
</ComboBox.GroupStyle>
<ComboBox.Style>
<Style TargetType="ComboBox">
<Setter Property="ItemsSource" Value="{Binding Path=Cars}" />
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsSelected, RelativeSource={RelativeSource AncestorType=DataGridCell}}" Value="True">
<Setter Property="ItemsSource" Value="{Binding Path=DataContext.GroupedCars, RelativeSource={RelativeSource AncestorType=DataGrid}}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>
The "Car" property for binding "SelectedItem" in combo box is an object of class "Car" holding some properties like id, name, etc.
The problem I am facing is that when I update the value of "Car" property and call "NotifyPropertyChanged" in its setter, then the value of "SelectedItem" in combo box goes blank/empty.
Please suggest.
The SelectedItem can no longer be found in the Collection (when you update your ItemSource) and gets set to null.
I've simplified your XAML to demonstrate
<ComboBox ItemsSource="{Binding Cars}"
SelectedItem="{Binding Car}">
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<Trigger Property="SelectedItem" Value="{x:Null}">
<Setter Property="SelectedIndex" Value="0" />
</Trigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>
Now the first Item will get selected when you update.
My combobox is bound to a list of states. The state have a column participating which when true the comboitem foreground color should be red. This works fine. But when I select the combobox item with foreground color red, it loses that foreground color and sets it to black. Can somebody help me point out what I am doing wrong?
<ComboBox Foreground="{Binding RelativeSource={RelativeSource AncestorType={x:Type ComboBoxItem}},Path=Foreground}"
DisplayMemberPath="StateName"
ItemsSource="{Binding States}"
SelectedValue="{Binding Model.StateID}" SelectedValuePath="StateID" >
<ComboBox.ItemContainerStyle>
<Style TargetType="{x:Type ComboBoxItem}">
<Setter Property="Foreground" Value="{Binding DoesNotParticipate, Converter={StaticResource NonParticipatingConverter}}"/>
</Style>
</ComboBox.ItemContainerStyle>
</ComboBox>
The binding you set for your ComboBoxes Foreground prop is looking for a ComboBoxItem typed ancestor in the visual tree, but the item you need is the descendant of the ComboBox. Especially the ComboBoxes SelectedItem.
EDIT
Since you bind the item to model objects the ComboBox.SelectedItems type would be this model objects type. Which means - probably - they don't have Foreground property.
I recommend the following:
It seems to me that DoesNotParticipate is a boolean prop so don't use Converter, use instead Trigger:
<ComboBox Foreground="{Binding RelativeSource={RelativeSource AncestorType={x:Type ComboBoxItem}},Path=Foreground}"
DisplayMemberPath="StateName"
ItemsSource="{Binding States}"
SelectedValue="{Binding Model.StateID}" SelectedValuePath="StateID" >
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=SelectedItem.DoesNotParticipate}" Value="True">
<Setter Property="Foreground" Value="Red"/>
</DataTrigger
</Style.Triggers>
</Style>
</ComboBox.Style>
<ComboBox.ItemContainerStyle>
<Style TargetType="{x:Type ComboBoxItem}">
<Style.Triggers>
<DataTrigger Property={Binding DoesNotParticipate} Value="True">
<Setter Property="Foreground" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.ItemContainerStyle>
</ComboBox>
I have a comboBox that is bound to a list of strings from my viewModel. What I am trying to do is have the foreground of a comboBox item be set to a different color if a property in my viewModel is true:
<ComboBox x:Name="myComboBox" ItemsSource="{Binding Names}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ...}">
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Style.Triggers>
<DataTrigger Binding="{Binding IsActive}" Value="True">
<Setter Property="Foreground" Value="Navy"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
I am not sure what to bind the Text of the TextBlock to. All I want is to display the list of strings. I always end up with a dropdown that has the items but they are not visible. I tried removing the style trigger thinking that maybe I was screwing up there, but that didn't help.
Am I taking the right approach? Will the ComboBox.ItemTemplate correctly look at my viewModel (which is the data context) when searching for IsActive or is that binding incorrect as well?
The DataContext for each ComboBoxItem is a string so
For the TextBlock, bind to the DataContext like Text="{Binding}
For the DataTrigger to be able to find IsActive, use RelativeSource in the binding
<ComboBox x:Name="myComboBox" ItemsSource="{Binding Names}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}">
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type ComboBox}},
Path=DataContext.IsActive}"
Value="True">
<Setter Property="Foreground" Value="Navy"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
When making controls non-amendable we display them as a TextBox to keep a consistent style. The problem is that a ComboBox can have any type of data so binding the Text property of the ControlTemplate TextBox is not as simple as using SelectedItem.
<Style TargetType="{x:Type ComboBox}">
<Style.Triggers>
<Trigger Property="IsReadOnly" Value="True">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<TextBox Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type ComboBox}}, Path=????, Converter={StaticResource ResourceKey=ComboToTextConverter}, UpdateSourceTrigger=PropertyChanged}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
The idea I have is to use a Converter and send the whole ComboBox so it can be handled by the Converter code. Is there anyway to do this?
Any other suggestions are welcome!
you need to use the SelectedValue and SelectedValuePath properties:
<Style TargetType="ComboBox" x:Key="cStyle">
<Style.Triggers>
<Trigger Property="IsReadOnly" Value="True">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ComboBox">
<TextBox Text="{Binding RelativeSource=
{RelativeSource TemplatedParent},
Path=SelectedValue}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
and heres your ComboBox
<ComboBox Name="cbox" ItemsSource="{Binding}"
Style="{StaticResource cStyle}"
SelectedValuePath="SomeText"
DisplayMemberPath="SomeText" />
now when you set the IsReadOnly property to true on the ComboBox, it turns into a TextBox with the selected value as its text.