Develop Reference

XAML/C# Hiding a TextBlock if the bound value is empty

in my WPF application I have a listview that only appears if a bound item has an values, this works like so
<ListView Grid.Row="1" Grid.Column="1" Margin="0,5,0,20" BorderThickness="0"
ItemContainerStyle="{StaticResource SelectionlessListViewItemStyle}"
ItemsSource="{Binding MissingAssets}">
<ListView.Style>
<Style TargetType="ListView">
<Style.Triggers>
<Trigger Property="HasItems" Value="False">
<Setter Property="Visibility" Value="Collapsed"></Setter>
</Trigger>
</Style.Triggers>
</Style>
</ListView.Style>
So this will only display the listview if MissingAssets has any values and works fine, above that I wanted a textblock as a header to just say "The following assets could not be found", and I want to hide this text of course if this listview is hidden too, I tried implementing it like this
<TextBlock Grid.Row="0" Grid.Column="1" VerticalAlignment="Center" FontWeight="Bold" Text="The following assets could not be found">
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Style.Triggers>
<DataTrigger Binding="{Binding MissingAssets}" Value="">
<Setter Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
But for some reason it won't hide even if MissingAssets is empty, I've tried using several different things in Value="" but nothing gets it to work. Is there a property or something I'm forgetting to set?
Thanks

You have many options here. The simplest should be to bind the TextBlock.Visibility to the ListView.Visibilty:
<StackPanel>
<TextBlock Visibility="{Binding Elementname="MissingAssetsListView", Path="Visbibility" />
<ListView x:Name="MissingAssetsListView" />
</StackPanel>

Found a workaround, I created a new string property in my C# code that remains blank unless missing assents are found, if they are found I populate the string and bind that string to a label in my XAML, so if the string is empty then there will be no visible label on the UI

Force focus on control via xaml style

I have a treeview and a listbox.
I want to specify on the style trigger-setter option that, when the listbox visibility is Hidden the focus have to return on the treeview.
Is it possibile to condition an user control focus on the state of another user control?
something like
<Style TargetType="{x:Type TreeView}">
<Style.Triggers>
<Trigger Property="Visibility" Value="Hidden">
<Setter Property="IsFocus" Value="True" />
</Trigger>
</Style.Triggers>
</Style>

Yes it is, see the example here
FOR CHILDREN IN CONTAINERS
<StackPanel FocusManager.FocusedElement="{Binding ElementName=lol}">
<TextBox x:Name="lol"/>
<TextBox x:Name="lul"/>
</StackPanel>
FOR SELF
<TextBox FocusManager.FocusedElement="{Binding RelativeSource={RelativeSource Self}}"/>

C# WPF - Change control content when another control event occurs

I'm quite new to WPF and MVVM and I'm trying to create a custom WindowChrome with all the standard Window features. I'm struggling with the Maximize/Minimize window Button content: I want the content to change when the user double clicks the WindowChrome bar, in order to show the right icon:
When I double click the bar, the result should be:
I managed to change the content with the Button Triggers, but how can I change it when another control event occurs?
Thanks in advance for the help!

Give the Button a Style with triggers that set the content based on the value of Window.WindowState. This isn't an event. The button reflects the current state of the window.
<Style TargetType="Button">
<Style.Triggers>
<DataTrigger
Binding="{Binding WindowState, RelativeSource={RelativeSource AncestorType=Window}}"
Value="Maximized">
<Setter Property="Content">
<Setter.Value>
<!-- I don't know if you're using a Path or what -->
<Path Stroke="White" Data="..." />
</Setter.Value>
</Setter>
</DataTrigger>
<DataTrigger
Binding="{Binding WindowState, RelativeSource={RelativeSource AncestorType=Window}}"
Value="Normal">
<Setter Property="Content">
<Setter.Value>
<!-- I don't know if you're using a Path or what -->
<Path Stroke="White" Data="..." />
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
It would be wiser to set the Template of the button instead, because there’s only one copy of each of those Paths, and if you reuse the style twice, they can’t be shared.
If there's some reason why this won't work with your code, show me your code.

Obscure / grey-out an inactive button

I want to make a button behave such that, if I do not click on dataGrid items the button is inactive. The code below works, but how do I obscure the button (shaded / greyed out)?
<Button x:Name="btDel" Height="22" Width="22" Click="btDel_Click" IsEnabled="False"
ToolTip="tooltip"
>
<Button.Content>
<Image Source="PNGImages/ItemDel.png"></Image>
</Button.Content>
<Button.Style>
<Style>
<Style.Triggers>
<DataTrigger
Binding="{Binding ElementName=dgTable,Path=SelectedIndex}"
Value="-1">
<Setter Property="Button.IsEnabled" Value="False"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>

Create your own style. This part ensures appearance of button when is disabled. <VisualState x:Name="Disabled">.
Default button style :
https://msdn.microsoft.com/en-us/library/ms753328%28v=vs.110%29.aspx
Usage :
<Button Style="{StaticResource _yourStyle}"
......
<Button/>

How to Change ContentControl `s Content on Toggle Button IsChecked Proprrty

Currently i am working on Changing the Content ( as image) of a container on toggle button IsChecked Proprty.
So i thought ContentControl would be a nice choice for a container. But i am not able to figure out how to achieve the result.
I created a resource of images in windows.resource
<Image Source="Resources/Desert.jpg" x:Key="image1"/>
<Image Source="Resources/Koala.jpg" x:Key="image2"/>
<Image Source="Resources/Lighthouse.jpg" x:Key="image3"/>
<Image Source="Resources/Chrysanthemum.jpg" x:Key="image4"/>
So i thought to Use the above resource to change the Content Property of a ContentControl by changing the ControlTemplate proprty by using Triggers where SourceName as (ToggleButton) and TargetName as (ContentControl) but its not working
SO how can I change the content of a ContentControl on toggleButton Ischeck property.
Edit
<ContentControl BorderBrush="Black" Name="cc">
<ControlTemplate>
<ControlTemplate.Triggers>
<Trigger SourceName="ToggleButton" Property="IsChecked" Value="True">
<Setter TargetName="cc" Property="Content" Value="{StaticResource image1}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</ContentControl>
I just tried as i have no idea how to do it.....
Any help are welcomed

You seem to have over complicated the situation unnecessarily. You can just use an Image control rather than a ContentControl. To alternate between two Images, you can simply do this with a DataTrigger:
<Image Source="Resources/Desert.jpg" x:Key="image1"/>
<StackPanel>
<ToggleButton Name="Button" Content="Change Image" Margin="10" />
<Image Margin="10,0,10,10">
<Image.Style>
<Style>
<Setter Property="Image.Source"
Value="/YourAppName;component/Resources/Desert.jpg" />
<Style.Triggers>
<DataTrigger Binding="{Binding IsChecked, ElementName=Button}"
Value="True">
<Setter Property="Image.Source"
Value="/YourAppName;component/Images/Resources/Koala.jpg" />
</DataTrigger>
</Style.Triggers>
</Style>
</Image.Style>
</Image>
</StackPanel>