Changing Text value of TextBlock embedded within a Control Template-CodePudding

I have a TextBlock that is inside a Control Template. I want to change the Text for said TextBlock with the Text value of a TextBox. The value is meant to be set within a button click event however, with the way I've tried to do this it doesn't work. The click event will give out an error stating that text is null.

I am new to WPF and would appreciate any help.

XAML for Control Template:

<Window.Resources>
    <ControlTemplate x:Key="panel" TargetType="Button">
        <Grid>
            <Rectangle x:Name="rectangle" Width="auto" Height="55" RadiusX="10" RadiusY="10"
                         Fill="White">
            </Rectangle>
            
            <TextBlock x:Name="txtBlk" Text="" Margin="10,10,0,0" />
        </Grid>
    </ControlTemplate>
</Window.Resources>

C# for Button_Click event

private void panelBtn_Click(object sender, RoutedEventArgs e)
{
    var text = (TextBlock)this.Template.FindName("txtBlk", this);
    text.Text = txtBox.Text;
}

CodePudding user response：

You should reference the template of the button like this..

private void panelBtn_Click(object sender, RoutedEventArgs e)
{
    if (sender is Button btn)
    {
        var text = btn.Template.FindName("txtBlk", btn) as TextBlock;
        text.Text = txtBox.Text;
    }
}

CodePudding user response：

@MuhammadSulaiman answered you correctly, but I would suggest that you change the implementation.
Rather than looking for an element in a template, it's better to add a resource to which this element will refer and change this resource.

<Window.Resources>
    <sys:String x:Key="button.Text">Some Text</sys:String>
    <ControlTemplate x:Key="panel" TargetType="Button">
        <Grid>
            <Rectangle x:Name="rectangle" Width="auto" Height="55" RadiusX="10" RadiusY="10"
                         Fill="White">
            </Rectangle>
            
            <TextBlock x:Name="txtBlk"
                       Text="{DynamicResource button.Text}" 
                       Margin="10,10,0,0" />
        </Grid>
    </ControlTemplate>
</Window.Resources>

private void panelBtn_Click(object sender, RoutedEventArgs e)
{
    if (sender is FrameworkElement elm)
    {
        elm.Resources["button.Text"] = txtBox.Text;
    }
}

You can also change the initial text in XAML:

    <Button Template="{DynamicResource panel}">
        <Buttun.Resources>
            <sys:String x:Key="button.Text">Other Text</sys:String>
        </Buttun.Resources>
    </Buttun>

In the same way, you can set a common initial text for all buttons located in one common container, through the resources of this container.