Question

How to make a button flat style in wpf?
I’ve tried BasedOn property but it does not work.

Answer 1

Just to get you started:

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Page.Resources>
    <Style x:Key="Flat">
        <Setter Property="Control.Background" Value="{x:Null}" />
        <Setter Property="Control.BorderBrush" Value="{x:Null}" />
        <Style.Triggers>
            <Trigger Property="Control.IsMouseOver" Value="True">
                <Setter Property="Control.Background" Value="{x:Null}" />
                <Setter Property="Control.BorderBrush" Value="{x:Null}" />
                <Setter Property="Control.FontWeight" Value="Bold" />
            </Trigger>
            <Trigger Property="Control.IsFocused" Value="True">
                <Setter Property="Control.FontWeight" Value="Bold" />
            </Trigger>
        </Style.Triggers>
    </Style>
  </Page.Resources>
  <StackPanel>  
    <Button Style="{StaticResource Flat}">Hello</Button>
  </StackPanel>
</Page>

Then you have one millon other ways to do it, even changing the ControlTemplate to complete redefine the Button