Why is null when requesting a style object?

Question

WPF

There is a style registered in resources.

<Window.Resources>
        
        <Style x:Name="NubmersStyle" TargetType="TextBlock" BasedOn="{StaticResource BaseFontFamily}">
            <Setter Property="Control.FontSize" Value="50"/>
            <Setter Property="Control.Background" Value="Transparent"/>
            <Setter Property="Control.HorizontalContentAlignment" Value="Center"/>
            <Setter Property="Control.VerticalContentAlignment" Value="Center"/>
            <Setter Property="Control.HorizontalAlignment" Value="Stretch"/>
            <Setter Property="Control.VerticalAlignment" Value="Stretch"/>
            <Setter Property="Control.Foreground" Value="white"/>
        </Style>


 </Window.Resources>

I am trying to change text color in code. To do this, Google quickly finds a solution that needs to be slightly changed and it turns out this

public void SetStyles()
        {
            Setter setter = new Setter(Control.ForegroundProperty, Color.FromArgb(0, 0, 0, 0));
            Style = Resources["NubmersStyle"] as Style;
            Style.Setters.Add(setter);
        }

It can be seen from it that I communicate with the resource dictionary by key, get an object and cast it to the Style type.
But only after type casting, I get null and when I add a new setter I get an error. From the debugger, you can see that there is a Resources dictionary and it even has a key called NubmersStyle. I guess that there is an error with type casting, but this is just a guess.

Answer 1

Alternatively, you can create a window in which to set predefined styles, set their TargetType and this should be done. Give each style a unique key. Create a property with the current style in the Code Behind of the window and change it. You can bind TextBlock to this property. You can make all this more beautiful, etc., but the essence of the example will be clear, I think.
Here you can see how Changing the styles at runtime in WPF is suggested here

<Window
    x:Class="Monitor.SomeWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:Monitor"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="SomeWindow"
    Width="800"
    Height="450"
    mc:Ignorable="d">
    <Window.Resources>
        <Style
            x:Key="BaseFontFamily"
            TargetType="TextBlock">
            <Setter Property="FontSize" Value="90" />
        </Style>
        <Style
            x:Key="Numbers1Style"
            BasedOn="{StaticResource BaseFontFamily}"
            TargetType="TextBlock">
            <Setter Property="Foreground" Value="LightCoral" />
        </Style>
        <Style
            x:Key="Numbers2Style"
            BasedOn="{StaticResource BaseFontFamily}"
            TargetType="TextBlock">
            <Setter Property="Foreground" Value="Bisque" />
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <TextBlock
            Grid.Row="0"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Style="{Binding TimeBlockStyle, RelativeSource={RelativeSource AncestorType=local:SomeWindow}}"
            Text="{Binding Path=RightTeam.TeamCounter, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
        <Button
            Grid.Row="1"
            Click="OnButtonClick" />
    </Grid>
</Window>

public partial class SomeWindow : Window
{
    public static readonly DependencyProperty TimeBlockStyleProperty = DependencyProperty.Register(
        nameof(TimeBlockStyle), typeof(Style), typeof(SomeWindow), new PropertyMetadata(default(Style)));

    public Style TimeBlockStyle
    {
        get { return (Style)GetValue(TimeBlockStyleProperty); }
        set { SetValue(TimeBlockStyleProperty, value); }
    }

    public SomeWindow()
    {
        InitializeComponent();
        TimeBlockStyle = (Style)Resources["Numbers1Style"];
    }

    private void OnButtonClick(object sender, RoutedEventArgs e)
    {
        TimeBlockStyle = (Style)Resources["Numbers2Style"];
    }
}

Answer 2

Resources["NubmersStyle"] is a typo. And the typo happened because of the magic words. They try not to write in this style in C#.