Setting Button FlatStyle in WPF

Add the following to your Window/Page resources:

<Style BasedOn="{StaticResource {x:Static ToolBar.ButtonStyleKey}}" TargetType="Button"></Style>

It will apply the flat style to all buttons in that styles scope.

The ToolBar class defines a Style that makes Buttons look flat. An example of using it is:

<Button Style="{StaticResource {x:Static ToolBar.ButtonStyleKey}}"/>

This also works for a ToggleButton when using ToggleButtonStyleKey.

WPF lets you completely restyle controls to make them look like whatever you want, which is why it doesn't have such a specific FlatStyle property on the Button control.