Develop Reference

Change Font Size of all UI Elements in using Static Resource from App.xaml in WPF

I'm need to change the font size of all text across the application.
I have tried doing as follows, but that doesn't work:-
<Style x:Key="fontsize" TargetType="{x:Type FrameworkElement}">
<Setter Property="Control.FontSize" Value="20"/>
</Style>
<Style TargetType="{x:Type FrameworkElement}" BasedOn="{StaticResource fontsize}"/>
When I try setting as follows then that works fine but doesn't get applied to all elements & needs to apply that for all different types of elements aperately.
<Style TargetType="TextBlock" BasedOn="{StaticResource fontsize}"/>
<Style TargetType="TextBox" BasedOn="{StaticResource fontsize}"/>
<Style TargetType="DataGridCell" BasedOn="{StaticResource fontsize}"/>
<Style TargetType="MenuItem" BasedOn="{StaticResource fontsize}"/>
<Style TargetType="DatePicker" BasedOn="{StaticResource fontsize}"/>
Also I would like to ask that, is there a way that I can override the Global Style for a particular element, like Heading text should be of different size on a user control?

in App.xaml
<Style TargetType="TextBlock">
<Setter Property="FontSize" Value="20"/>
<Setter Property="FontWeight" Value="Bold"/>
</Style>

Create a global style for the window in App.xaml.
<Application.Resources>
<Style x:Key="WindowStyle" TargetType="{x:Type Window}">
<Setter Property="FontStyle" Value="Italic" />
<Setter Property="FontSize" Value="24" />
<Setter Property="Foreground" Value="Green"/>
</Style>
</Application.Resources>
and set that style for the required windows.
<Window x:Class="YourNamespace.MainWindow" Style="{StaticResource WindowStyle}".....>
for overriding the style for a usercontrol
<local:UserControl1>
<local:UserControl1.Style>
<Style TargetType="UserControl">
<Setter Property="FontSize" Value="10"/>
</Style>
</local:UserControl1.Style>
</local:UserControl1>

There are two controls this involves.
You're maybe thinking "hey what about this cell or that calendar".
Their templates show text in a textblock.
When you set Header on a menuitem or content on a label, you get a textblock generated.
You therefore "only" need to set style on both textblock and textbox:
<Application.Resources>
<ResourceDictionary>
<Style TargetType="TextBlock">
<Setter Property="FontSize" Value="20"/>
</Style>
<Style TargetType="TextBox">
<Setter Property="FontSize" Value="20"/>
</Style>
</ResourceDictionary>
</Application.Resources>
</Application>
Having said that.
As Clemens pointed out.
The Font size and styling dependency properties are marked as inherits, so if you just have mainwindow then you could just set on that.
It's not just "obvious" that a label ends up with a textblock in it when you set content though. Similarly a menuitem and header. Hence I thought it worth posting this answer.

WPF - Change Scrollbar's margin of a TextBox using Styles

I have a defined an implicit style for Scrollbar and set some properties and I use it for most ScrollViewrs. Part of the Style is :
<Style x:Key="{x:Type ScrollBar}" TargetType="{x:Type ScrollBar}">
<Setter Property="Background" Value="#FF283542" />
<Setter Property="Margin" Value="0,-32,0,0" />
<Setter Property="Width" Value="5" />
</Style>
But I have some TextBoxes which I want them to have the same implicit Scrollbar style for their Scrollbars but with a diffrent margin.
I can do it by adding Resources to every TextBox and override the implicit ScrollBar style like :
<TextBox Style="{StaticResource big-text-style}">
<TextBox.Resources>
<Style TargetType="{x:Type ScrollBar}"
BasedOn="{StaticResource {x:Type ScrollBar}}">
<Setter Property="Margin" Value="0"/>
</Style>
</TextBox.Resources>
</TextBox>
This code gives me the functionality I want. But the problem with this approach is that I have to write these lines of code of every TextBox! It would be much better if I could put this as part of the TextBox style itself.
I wonder is there a way to put it in the TextBox's Style so that every TextBox which has big-text-style(for example), have the overriden ScrollBar ?
Or is there a better way to implement this kind of thing ?
Thank you for the help!

You can add the overriding ScrollBar style to the Resources of the TextBox style itself:
<Style x:Key="big-text-style" TargetType="TextBox">
<Style.Resources>
<Style TargetType="{x:Type ScrollBar}" BasedOn="{StaticResource {x:Type ScrollBar}}">
<Setter Property="Margin" Value="0"/>
</Style>
</Style.Resources>
</Style>

WPF Setter not working on some controls

I am trying to use a setter in my application to change to font size of all Controls. My Style is looking like this:
<Style x:Key="baseStyle" TargetType="{x:Type Control}">
<Setter Property="FontSize" Value="12" />
<Setter Property="Background" Value="{x:Null}" />
<Style.Triggers>
<DataTrigger Binding="{Binding Width, ConverterParameter=1000, Converter={StaticResource DoubleToBoolConverter}, ElementName=window, Mode=OneWay}" Value="True">
<Setter Property="FontSize" Value="24" />
<Setter Property="Background" Value="Red" />
</DataTrigger>
</Style.Triggers>
</Style>
All of my substyles are looking like this
<Style BasedOn="{StaticResource baseStyle}" TargetType="{x:Type Button}">
...
</Style>
My problem is that my styles isnot applied to all controls. Labels for example seam to ignore my FontSize Setter
Default Style:
Triggered Style:

Do you actually refer to Label elements or TextBlock elements? Because the latter type is not a Control and won't be affected by your Style. This should work though:
<Style BasedOn="{StaticResource baseStyle}" TargetType="{x:Type Label}" />
But please always remember to provide a reproducible sample of your issue when asking a question: https://stackoverflow.com/help/mcve

How can I stop ToolTips from inheriting my TextBlock style?

I've defined a style within my application resources that I want all of my textblocks to inerit :
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Effect">
<Setter.Value>
<DropShadowEffect BlurRadius="1" ShadowDepth="0" />
</Setter.Value>
</Setter>
<Setter Property="Foreground" Value="White" />
<Setter Property="FontFamily" Value="Arial" />
<Setter Property="FontWeight" Value="Bold" />
</Style>
I don't want to have to go through and explicitly dictate the style on each textblock - I just want all of them to inherit this style naturally.
Unfortunately, when I define a tooltip, that tooltip also picks up this style. I'm guessing it's because the thing incorporates a TextBlock somewhere in it's design.
What I AM okay with is having to go through and style each defined tooltip ( since they are used less ubiquitously throughout my application ), so if there's some way to define a tooltip style that will override the inherited textblock style, I'm fine with that.
So, what can I do to stop my tooltips from inheriting the TextBlock style?

It's a terrible idea to set a global implicit style on TextBlock, and this is why. TextBlock is the primitive that displays text. It's much better to set the implicit TextBlock style only where it's needed, not universally.
Or consider using Label instead of TextBlock for the styled text instances, and have an implicit Label style. That's one reason why Label exists. You can style the padding/margin etc. to make it look exactly the way you want.
But if you want the quick and dirty and easy way to work around a bad decision, you can use the implicit-style-localized-within-a-style trick that grandpa used to flummox General Rommel at El Alamein:
<Style TargetType="ToolTip">
<Style.Resources>
<!-- Implicit style for TextBlocks within ToolTips -->
<Style TargetType="TextBlock">
<Setter Property="Foreground" Value="Black" />
<Setter Property="FontWeight" Value="Regular" />
<Setter Property="Effect" Value="{x:Null}" />
</Style>
</Style.Resources>
<Setter Property="Foreground" Value="Black" />
<Setter Property="FontWeight" Value="Regular" />
<Setter Property="Effect" Value="{x:Null}" />
</Style>

WPF DatePicker Popup Calendar Background Color

How can I style the background color of the popup / dropdown control of the default WPF DatePicker control?
I want to do this via xaml.
This does not work:
<Style TargetType="{x:Type DatePicker}">
<Setter Property="FontFamily" Value="/fonts/#Titillium Web" />
<Setter Property="VerticalAlignment" Value="Center" />
<Setter Property="Background" Value="#777777" />
</Style>
I assume that it does not target the right property.
This is how it currently looks. I want to change the white background to something readable.

Try targeting DatePickerTextBox, like so:
<Style TargetType="{x:Type DatePickerTextBox}">
<Setter Property="Background" Value="#777777" />
</Style>