CODEWITHSUNDEEP
wpfxamluser-controls
Alan Wayne
Alan Wayne

Reputation: 5394

How is OnApplyTemplate() used for a UserControl?

I have not been able to find any examples of this. Having a UserControl defined below with the customcontrol, SimpleTextBlock (that inherits from TextBlock), I would like to use the OnApplyTemplate() event in the usercontrol code-behind to grab some of the properties known only to the SimpleTextBlock only after being rendered at run-time.

This code does not work. How is this done?

  XAML

    <UserControl x:Class="Nova5.UI.Views.Ink.InkEditorView"
              ..........
    <Grid Background="#FFE24848" >
              ..........

      <Canvas Grid.Row="1" Grid.RowSpan="3">

        <ScrollViewer VerticalScrollBarVisibility="Auto" 
            Width="{Binding Parent.ActualWidth, Mode=OneWay, RelativeSource={RelativeSource Self}}"
            Height="{Binding Parent.ActualHeight, Mode=OneWay, RelativeSource={RelativeSource Self}}">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition Height="100"/>
                </Grid.RowDefinitions>


                <fsc:SimpleTextBlock x:Name="PART_SimpleTextBlock"
                 Background="#FFE24848"
                 RichText="{Binding     RichText, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"                 
                 FontSize="{Binding     FontSize, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}" 
                 FontStyle="{Binding   FontStyle, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"
                 FontWeight="{Binding FontWeight, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"   
                 FontFamily="{Binding FontFamily, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"   
                  />
            </Grid>
        </ScrollViewer>
    </Canvas>
</Grid>


    C# code-behind:

      [TemplatePart(Name = "PART_SimpleTextBlock", Type = typeof(TextBlock))]
public partial class InkEditorView : UserControl
{

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        *** t IS NULL ????
        SimpleTextBlock t = (SimpleTextBlock)base.GetTemplateChild("PART_SimpleTextBlock");


   }

What am I missing? (Be kind :) ) Thanks for any help.

Upvotes: 3

Views: 4449

Answers (1)

Justin XL
Justin XL

Reputation: 39006

OnApplyTemplate only works inside a custom control, not a usercontrol. :)

Your C# code is the implementation of a custom control however your xaml code is to create a usercontrol.

Basically, a usercontrol is what you use to group a few controls and panels together while a custom control is just like a Button, a CheckBox or a ListView. Normally you want to create a custom control when you want to extend an existing control. In your case, looks like you want to extend the UserControl.

This link has a comparison between them too and also a good example of how to create one.

Upvotes: 4

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