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

Using custom properties in WPF styles

I have this text box:
<TextBox/>
I want to add a watermark to it to say, Enter your message here...
Since its not supported out of the box, this successfully does the trick:
<Style TargetType="TextBox" xmlns:sys="clr-namespace:System;assembly=mscorlib">
<Style.Resources>
<VisualBrush x:Key="CueBannerBrush" AlignmentX="Left" AlignmentY="Center" Stretch="None">
<VisualBrush.Visual>
<Label Content="Enter your message here..." Foreground="LightGray" Padding="10 0 0 0" />
</VisualBrush.Visual>
</VisualBrush>
</Style.Resources>
<Style.Triggers>
<Trigger Property="Text" Value="{x:Static sys:String.Empty}">
<Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
</Trigger>
<Trigger Property="Text" Value="{x:Null}">
<Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="True">
<Setter Property="Background" Value="White" />
</Trigger>
</Style.Triggers>
</Style>
But is there a way to extend TextBox with a XAML property for WatermarkText, as follows and have my style pick it up and use it, or is there some other way to do it (C#, etc.)?
<TextBox WatermarkText="Enter your message here..."/>

The best way to do this is using Attached Dependency Properties that you can bind in the style. Just keep in mind that binding an attached dependency property is
Text={Binding (AttachedPropertyName)}
The () make the trick.
Have a look at Mahapps. It's a nice design framework and providing a TextBoxHelper class doing all this. It's open source so you can see how it is implemented using attached properties.

The easiest way to do what I need is to just put a label in the same position as the text box without hit test visibility in the .xaml:
<TextBox Name="Username" Grid.Row="2" Height="40" FontFamily="Segoe UI" FontSize="20" VerticalContentAlignment="Center" TextChanged="Username_TextChanged"/>
<Label Name="UsernameLabel" Content="Username" Grid.Row="2" FontFamily="Segoe UI" FontSize="20" Foreground="LightGray" Padding="5" IsHitTestVisible="False" />
In the .cs:
private void Hostname_TextChanged(object sender, TextChangedEventArgs e)
{
UpdateLabel(Hostname, HostnameLabel);
}
private void UpdateLabel(TextBox textBox, Label label)
{
label.Visibility = String.IsNullOrWhiteSpace(textBox.Text) ? Visibility.Visible : Visibility.Hidden;
}
This works for password boxes too, which are sealed, so you cannot inherit them anyways if you tried to extend sealed controls.

WPF ComboBox EditTemplate - TextBox border is not going away

I am using a DEVExpress combobox and have enabled type ahead (Auto search functioanlity). In combo box I am showing two things. First item is an image and second item is a value(id).
Mine problem is that the value border is getting outside to combo box while showing at UI at run time. I tried setting margin but its of no use. My application is having option to select theme and for some of the theme its getting hazy.
Any idea how to get rid of this ?
see the first one is looking fine however the below one is bit hazy if i change the theme.
I am using below code for the same.
<dvEx:ComboBoxEdit.EditTemplate>
<ControlTemplate>
<StackPanel Orientation="Horizontal">
<Image Source="{Binding Path=(dxe:BaseEdit.OwnerEdit).SelectedItem.Image, RelativeSource={RelativeSource Self}}" Margin="8, 0, 4, 0"/>
<TextBox x:Name="PART_Editor" BorderBrush="Transparent"/>
</StackPanel>
</ControlTemplate>
</dvEx:ComboBoxEdit.EditTemplate>
<dvEx:ComboBoxEdit.ItemTemplate>
<DataTemplate DataType="{x:Type vm:DesignSelectViewModel}">
<StackPanel Orientation="Horizontal">
<Image Source="{Binding Image}" Margin="8, 0, 4, 0"/>
<TextBlock Text="{Binding Name}"/>
</StackPanel>
</DataTemplate>
</dvEx:ComboBoxEdit.ItemTemplate>

To accomplish your task I suggest you to override the TextBox.Template as follows to make it theme-independent and remove it's focused state (border and background):
<TextBox x:Name="PART_Editor">
<TextBox.Template>
<ControlTemplate TargetType="{x:Type TextBox}">
<Grid x:Name="Root" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}">
<ScrollViewer x:Name="PART_ContentHost" Margin="1" Padding="{TemplateBinding Padding}"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsReadOnly" Value="True">
<Setter Property="Opacity" TargetName="PART_ContentHost" Value="0.75"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Opacity" TargetName="Root" Value="0.5"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</TextBox.Template>
</TextBox>
Related MSDN article: TextBox Styles and Templates

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>

WPF ItemsControl IsMouseOver not working as expected

I have the following code in the Window.Resources of a WPF window. What it is basically doing is creating an item that represents a grid with a label positioned on the left and a button on the right. When I mouse over the label or the button the row changes color as expected but I want it to also change color if the mouse is over any of the row.
How can this be achieved?
Any help is appreciated.
<Window.Resources>
<dtos:ProjectDto x:Key="data"/>
<Style x:Key="alternatingWithTriggers"
TargetType="{x:Type ContentPresenter}">
<Setter Property="Height" Value="25"></Setter>
</Style>
<Style x:Key="onmouseover" TargetType="{x:Type DockPanel}">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="Yellow">
</Setter>
</Trigger>
</Style.Triggers>
</Style>
<DataTemplate x:Key="ItemTemplate">
<Border x:Name="ItemBorder" HorizontalAlignment="Stretch" BorderThickness="0" Background="#BBB" ClipToBounds="True" >
<DockPanel ClipToBounds="True" HorizontalAlignment="Stretch" Style="{StaticResource onmouseover}">
<Label Content="{Binding Name}" HorizontalAlignment="Left" Height="80"></Label>
<Button Content="Delete" HorizontalAlignment="Right" Margin="0,0,10,0"/>
</DockPanel>
</Border>
...

Give the DockPanel Background="Transparent". That should allow it to capture mouse events.

I don't see anything obviously wrong in the snippet you've posted, and since I'm not in front of Studio, I can't try it out, but if I were you, I'd try adding a MouseEnter handler on the DockPanel (just throw the do-nothing handler in the code-behind for the view, since you'll remove it later).
Make sure that handler is getting hit when you enter, and with the debugger/immediate window, make sure the IsMouseOver property is as you expect it to be. That will at least direct your next debugging steps:
If IsMouseOver is true and your handler is hit, then my guess would be something about the trigger you've got set up isn't quite right.
If IsMouseOver is false or your handler isn't hit, then my guess would be something like IsHitTestVisible is set to false or something of that sort.
Just for fun, I'd also try moving the style declaration inline to the dockpanel, just to make sure, like so:
<DataTemplate x:Key="ItemTemplate">
<Border x:Name="ItemBorder" HorizontalAlignment="Stretch" BorderThickness="0" Background="#BBB" ClipToBounds="True" >
<DockPanel ClipToBounds="True" HorizontalAlignment="Stretch">
<DockPanel.Style>
<Style TargetType="{x:Type DockPanel}">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="Yellow"/>
</Trigger>
</Style.Triggers>
</Style>
</DockPanel.Style>
<Label Content="{Binding Name}" HorizontalAlignment="Left" Height="80"></Label>
<Button Content="Delete" HorizontalAlignment="Right" Margin="0,0,10,0"/>
</DockPanel>
</Border>