Binding dynamic Style to UserControl

Question

I try to change the Textsize based on a slider on the mainpage.

<Window.Resources>

    <Style TargetType="TextBlock">
      <Setter Property="TextBlock.FontSize" Value="{Binding ElementName=sliderFontsize, Path=Value}/>
    </Style>

So on the mainpage its displayed ok. The usercontrol embedded on the mainpage somehow did not get the changed fontsize at all. It complains that it could not find the bound property :

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'ElementName=sliderFontsize'. BindingExpression:Path=Value; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'FontSize' (type 'Double')

Binding is still a bit magic to me :)

Answer 1

Try this:

<Window x:Class="WpfApplication1.Window1"
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 xmlns:local="clr-namespace:WpfApplication1" 
 Title="MainWindow" Height="350" Width="400">
 <Window.Resources>
 <Style TargetType="TextBlock">
  <Setter Property="TextBlock.FontSize" Value="{Binding ElementName=sliderFontSize,Path=Text }"/>
 </Style>
 </Window.Resources>
 <StackPanel>
 <TextBlock Height="21" Width="100" Text="My Text"/>
 <TextBox Height="21" Width="100" Name="sliderFontSize" />
 </StackPanel>
</Window>

 

sliderFontSize Control should be visible to the TextBlock control.

Answer 2

The sliderFontSize control which is present in Main Page will not be visible to a textBlock inside your UserControl. You will have to bind your textblock to a Property visible across the application. i.e. sliderFontSize to a CustomObject(Application Level) and that CustomObject you can bind to the application level resource.

Answer 3

Hi Shalan007,

Since the DataBinding can fine the element named sliderFontSize in the UserControl.

You could create a property and bind it to the TextBox.Text and the Style for the TextBlock. The property looks like a bridge connect the TextBox.Text and the Style:

 <Window.Resources>
  <Style TargetType="TextBlock">
   <Setter Property="TextBlock.FontSize" Value="{Binding FontSize}"/>
  </Style>
 </Window.Resources>
 <StackPanel>
  <TextBlock Text="aaaa"/>
  <l:UserControl1/>
  <TextBox Text="{Binding fontSize, UpdateSourceTrigger=PropertyChanged}"/>
 </StackPanel>

Code:

 public partial class Window2 : Window
 {
  public int fontSize { get; set; }
  public Window2()
  {
   InitializeComponent();
   this.DataContext = this;
  }
 }

Hope this helps.

Sincerely,

Bob Bao

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Answer 4

Thx. I'll try that one out.
Currently I am using code behind to update teh FontSize properties of my usercontrols manually...

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