Set Font Size Dynamically in WPF

Question

I'm trying to set font size dynamically in WPF. Here what i did so far.

App.xaml

<Style TargetType="{x:Type FrameworkElement}" x:key="baseStyle"></Style>
<Style TargetType="{x:Type TextBlock}" BasedOn={StaticResource baseStyle}"/>

App.xaml.cs

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
         base.OnStartup(e);
         double fontSize = System.Drawing.SystemFonts.IconTitleFont.Size;
         Style style = new Style{ TargetType = typeof(FrameworkElement)};
         style.Setter.Add(new Setter(TextElement.FontSizeProperty, fontSize));
       Application.Current.Resources["baseStyle"] = style;  

    }
}

MainWindow.xaml

<TextBlock Text="This is Sparta!!!"/>

Issue:

When the OnStartup called the resource 'baseStyle' is not available. So the style is assigned to Null value due to which the style is not applied. Anyone having idea to implement it in some other way. Your help will be appreciated.

Edit: There is one thing that i would like to clarify. In reality i have wrote that App.xaml and App.xaml.cs code in resource dictionary and merged it in App.xaml. The code written in OnStartup is written in constructor of that code behind class.

Maybe helpful: stackoverflow.com/a/65626626/6859121

Mr. Squirrel.Downy
– Mr. Squirrel.Downy

2021-11-16 02:16:32 +00:00
Commented Nov 16, 2021 at 2:16 — Mr. Squirrel.Downy
– Mr. Squirrel.Downy, Commented Nov 16, 2021 at 2:16

score 1 · Accepted Answer · 2016-04-27 12:38:21Z

1

With a little modification your code works. Just remove and add the base style

Style style = new Style { TargetType = typeof(FrameworkElement) };
            style.Setters.Add(new Setter(TextElement.FontSizeProperty, fontSize));
            Application.Current.Resources.Remove("baseStyle");
            Application.Current.Resources.Add("baseStyle" , style);

edited Apr 27, 2016 at 12:38

answered Apr 27, 2016 at 12:07

user5747953

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3 Comments

Zeb-ur-Rehman Over a year ago

Well that's not an issue brother i already did that. The issue is that it didn't pick up the code behind style.

Zeb-ur-Rehman Over a year ago

Thank you very for your effort, but that didn't worked too. If you want to confirm just add this line to your code style.Setters.Add(new Setter(TextElement.BackgroundProperty, Brushes.Azure)); The color wont change.

Zeb-ur-Rehman Over a year ago

In that case program throws an error Can only base on a Style with target type that is base type 'TextBlock'

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