Develop Reference

How to collapse contents of a databound ListBoxItem when a button is clicked in WPF MVVM

I have a ListBox in my WPF MVVM app using the following code:
<GroupBox Grid.Column="0" Margin="0,0,0,-58">
<DockPanel>
<TextBlock DockPanel.Dock="Top"
HorizontalAlignment="Center"
Margin="0,0,0,8"
FontWeight="Bold"
Text="{x:Static p:Resources.AvaliableLEDsLabel}" />
<ListBox Name="AvailableLEDsListbox" SelectionMode="Extended"
dd:DragDrop.IsDragSource="True"
dd:DragDrop.IsDropTarget="True"
dd:DragDrop.DropHandler="{Binding}"
ItemTemplate="{StaticResource DataTemplateListBoxItem}"
ItemsSource="{Binding AvailableLeds}"
ScrollViewer.VerticalScrollBarVisibility="Hidden"
>
<ListBox.GroupStyle>
<StaticResource ResourceKey="StyleListBoxGroup" />
</ListBox.GroupStyle>
</ListBox>
</DockPanel>
</GroupBox>
This displays grouped lists of devices, with LEDs under them. The DataTemplate is the following:
<GroupStyle x:Key="StyleListBoxGroup">
<GroupStyle.HeaderTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Button Command="{Binding HideGroupCommand}">X</Button>
<TextBlock VerticalAlignment="Center"
HorizontalAlignment="Left"
FontWeight="Bold"
Text="{Binding Name}" />
</StackPanel>
</DataTemplate>
</GroupStyle.HeaderTemplate>
</GroupStyle>
<DataTemplate x:Key="DataTemplateListBoxItem">
<TextBlock x:Name="LedId" Text="{Binding LedId}"/>
</DataTemplate>
I would like to make the X button in the header hooked up to the HideGroupCommand toggle the hiding of all the items under that particular header. How would I go about doing this? Thanks in advance.

You have few options.
First one :
You would need to have a property in your view model something like 'ListBoxVisibility' then u would bind that property to your UI. In command text u just changed visibility property of that property in view model- so u have it reflected on UI. This visibility property can be of type 'bool' , or 'Visibility' or whatever. Only if it's type of Visibility u don't need converter when binding.
NOTE : Some people use it - even though it kinda goes out of general principel of MVVM patter. But sometimes u have to do it.
Second
If wanna stick to MVVM , then u need to fully separate your UI from your viewmodel. Create click event and change visibility.

Windows Store App - XAML UI element not visible in C# code

I have the following XAML code and the only element available in the C# code behind are the Grid and the FlipView. How can I make the ScrollViewer, Image or the Viewbox visibile in the code?
XAML:
<Grid x:Name="gridViewPages">
<FlipView x:Name="FlipView1" Loaded="FlipView1_Loaded" Style="{StaticResource FlipViewPreviewIndicator}" Tapped="FlipView1_Tapped">
<FlipView.ItemTemplate>
<DataTemplate>
<ScrollViewer x:Name="pagesScrollViewer" ZoomMode="Enabled"
HorizontalAlignment="Center"
VerticalAlignment="Center"
HorizontalScrollBarVisibility="Hidden"
VerticalScrollBarVisibility="Hidden"
MinZoomFactor="1.0"
MaxZoomFactor="3.0"
Margin="0"
Width="1500" DoubleTapped="PagesScrollViewer_DoubleTapped">
<Viewbox x:Name="pagesViewbox">
<Image Source="{Binding}"
Height="730"
x:Name="pageImage" Stretch="Uniform" Loaded="MainImage_Loaded"/>
</Viewbox>
</ScrollViewer>
</DataTemplate>
</FlipView.ItemTemplate>
</FlipView>
</Grid>
The flipview is customized and contains also a listview defined in which is not visible in the code too...:
<Page.Resources>
...
<ListView x:Name="pagesPreview" HorizontalAlignment="Center" Height="100" VerticalAlignment="Bottom" Width="Auto"
ItemsSource="{TemplateBinding ItemsSource}"
SelectedItem="{Binding SelectedItem, Mode=TwoWay, RelativeSource={RelativeSource Mode=TemplatedParent}}"
ScrollViewer.HorizontalScrollBarVisibility="Auto"
ScrollViewer.VerticalScrollBarVisibility="Disabled"
ScrollViewer.HorizontalScrollMode="Enabled"
ScrollViewer.VerticalScrollMode="Disabled"
Background="AliceBlue"
Opacity="1"
SelectionChanged="pagesPreview_SelectionChanged"
Visibility="Visible">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemTemplate>
<DataTemplate>
<Grid HorizontalAlignment="Center" VerticalAlignment="Center">
<Image Source="{Binding}" Stretch="UniformToFill"/>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
...
</Page.Resources>

See the basic concept of the flipview is to have multiple pages to have a flip effect. So whatever the Data template contains is repeated multiple times. So if you want the x:Name to come up then you wont have any success.
There are two ways As per my knowledge :
VisualTreeHelper -> for a better detail of it go through this link
Get elements from data template
you can manually iterate over the flipview elements and track down the children of the flipview. Try that in debug mode you'll get a fair idea of what comes after what. Just keep track of the element at which selected index position you want modified
Thanks.

How to show a list of items?

I need to show a list of tweets. each tweet can be highlighted programmatically and also I can add some new controls to the tweet item. and I am using data binding.
for my purpose above, I thought of using a LongListSelector but it is too buggy, and it seems that I can't access a collection of its items (can I?). what else is suitable for showing a list of items, each item can contain some other controls, and also supports binding? I don't see another thing in the toolbox? is there any ester egg?
It's windows phone 8 app.

You can use a ListBox
<ListBox Name="listboxTimeline" Width="450" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Margin="0,5,0,5" >
<Button Click="btn1_Click" >
<StackPanel VerticalAlignment="Top">
<Image Name="image" Source="{Binding ImageSource}" />
</StackPanel>
</Button>
<StackPanel Width="337">
<TextBlock Text="{Binding UserName}" />
<TextBlock Text="{Binding Content}" TextWrapping="Wrap" />
</StackPanel>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
And then you can data bind to this from your CS page. ( The above code is just a sample)

Accessing group-headings sub elements in data-bound GridView

I'm developing a windows 8 metro application with a data-bound gridview xaml control.
I've added a ring progress bar named progressRingGroup to header of the groups as seen below.
<ProgressRing x:Name="progressRingGroup" IsActive="True" Visibility="Visible" Width="16" Height="16" Margin="0,-7,0,0"/>
I want to programmatically access the ring-progress-bar from my code (so I can start/stop it) but as my grid-view is databound I don't know how to do so.
I've multiple groups in the gridview and need to access all of them separately.
Here's my gridview's groupstyle xaml definition;
<GridView.GroupStyle>
<GroupStyle>
<GroupStyle.HeaderTemplate>
<DataTemplate>
<Grid Margin="1,0,0,6">
<Button
AutomationProperties.Name="Group Title"
Click="Header_Click"
Style="{StaticResource TextPrimaryButtonStyle}" >
<StackPanel Orientation="Horizontal">
<ProgressRing x:Name="progressRingGroup" IsActive="True" Visibility="Visible" Width="16" Height="16" Margin="0,-7,0,0"/>
<TextBlock Text="{Binding Title}" Margin="6,-7,10,10" Style="{StaticResource GroupHeaderTextStyle}" />
<TextBlock Text="{StaticResource ChevronGlyph}" FontFamily="Segoe UI Symbol" Margin="0,-7,0,10" Style="{StaticResource GroupHeaderTextStyle}"/>
</StackPanel>
</Button>
</Grid>
</DataTemplate>
</GroupStyle.HeaderTemplate>
<GroupStyle.Panel>
<ItemsPanelTemplate>
<VariableSizedWrapGrid ItemWidth="75" ItemHeight="150" Orientation="Vertical" Margin="0,0,80,0" MaximumRowsOrColumns="3"/>
</ItemsPanelTemplate>
</GroupStyle.Panel>
</GroupStyle>
</GridView.GroupStyle>
Help appreciated.

If you want to be able to control the IsActive property of each progress ring, add a bool property to your group data model, and bind IsActive to that property. That way you can control each ProgressRing without having to programatically access all of them.
For example:
<ProgressRing x:Name="progressRingGroup" IsActive="{Binding GroupLoading}" Visibility="Visible" Width="16" Height="16" Margin="0,-7,0,0"/>
If you still want to access each programmatically, you could assign a Loaded event to the ProgressRing in the DataTemplate, and when the event fires, grab a reference to the ring (sender).

ScrollViewer in a listbox

I´m filling a listbox with a specific data, the code works fine, but I need to add a scrollviewer to the listbox because there are many elements inside, I tried to use a ScrolViewer and put inside the listbox, but doesn't work, here is the code
<StackPanel x:Name="Sites" Grid.Row="1" Orientation="Vertical">
<ListBox x:Name="ListSites" >
<ListBox.ItemTemplate>
<DataTemplate>
<Button Width="460" Height="120" Click="click" Name="btn">
<Button.Content>
<StackPanel Orientation="Vertical" Height="100" Width="460">
<TextBlock Width="460" Name="txtname" FontSize="22" Text="{Binding name}" Height="40" Foreground="CadetBlue" />
<TextBlock Width="460" Name="txtUrl" FontSize="22" Text="{Binding Url}" Height="60"/>
</StackPanel>
</Button.Content>
</Button>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>

I fixed it, simply adding the Height property in the ListBox control

If the ListBox is not given infinite space for height then it should automatically scroll when items overflow its boundaries. For instance, if the second Grid row outside your stackpanel has explicit or 'star' height set, the scrollbar in the listbox will show up automatically.
See also: Silverlight: Difficulty with ScrollViewer

You shouldn't need to add a ScrollViewer to your ListBox. It will start scrolling when it runs out of room.
However, because you've put the ListBox inside a StackPanel it won't ever think it's run out of room because the StackPanel grows infinitely in the direction of it's orientation to accommodate its contents.
You'll need to use a different container for your ListBox.

<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>