ContentSelector WPF

Question

I want to set a different content Template inside a button, to act like a Toggle Button, depending on the state of my ViewModel. I have simplified the code quite a bit, but in each Data Template the button's content draws different Path Geometries, together with a textblock.

ContentSelector class:

public class ContentSelector : DataTemplateSelector {
    public DataTemplate TrueTemplate { get; set; }
    public DataTemplate FalseTemplate { get; set; }

    public override DataTemplate SelectTemplate(object item, DependencyObject container) {
        if ((bool)item)
            return TrueTemplate;
        return FalseTemplate;
    }
}

Edit: Added properties to the button to set its content, where 'State' isa boolean value in my ViewModel, and the converter is just returning 'T' or 'F', based on the State of my ViewModel

XAML:

<DataTemplate x:Key="HeaderTemplate">
    <ContentPresenter>
        <ContentPresenter.Content>
            <DockPanel LastChildFill="False">
                <Button  Content="{Binding State, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ButtonContentConverter}}" Command="{Binding ToggleCommand}">>
                    <Button.ContentTemplateSelector>
                        <ContentSelector>
                            <local:ContentSelector.TrueTemplate>
                                <DataTemplate>
                                    <TextBlock Text="T" ... />
                                </DataTemplate>
                            </local:ContentSelector.TrueTemplate>
                            <local:ContentSelector.FalseTemplate>
                                <DataTemplate>
                                    <TextBlock Text="F" ... />
                                </DataTemplate>
                            </local:ContentSelector.FalseTemplate>
                        </ContentSelector>
                    </Button.ContentTemplateSelector>
                </Button>
            </DockPanel>
        </ContentPresenter.Content>
    </ContentPresenter>
</DataTemplate>

I cannot seem to hit the breakpoint in my ContentSelector class. It does work in the designer, meaning the button's content changes to 'T' or 'F' if I change it to return the corresponding DataTemplate in the ContentSelector Class, but when I run the application it never hits the ContentSelector, and the content of the button is completely empty.

Any ideas as to why this would happen? I have tried setting the Content of the button to the State of my ViewModel, and changing that to a boolean value using a converter, thinking that the content of the button must be set to trigger the ContentSelector, but it didnt work.