WPF style present different while apply for multiply control - wpf

Question

I have two button with the code in xaml is:
<Button Grid.Row="0" Grid.Column="2" Style="{StaticResource styleInfomationButton}" />
<Button Grid.Row="1" Grid.Column="2" Style="{StaticResource styleInfomationButton}" />
They're same style, but in runtime they were presented differently:
Here the image how the form showed:
Style applied:
<Style x:Key="styleInfomationButton" TargetType="Button">
<Setter Property="Width" Value="22" />
<Setter Property="Height" Value="22" />
<Setter Property="Content">
<Setter.Value>
<TextBlock FontWeight="ExtraBold" Foreground="White">?</TextBlock>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Grid Width="20" Height="20">
<Ellipse Fill="#81A9F0" />
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 1

When I tried the above code, it failed at runtime with the error:
Specified element is already the logical child of another element. Disconnect it first
Then, I looked at the code again and see you are setting Content property in the style. When you tried to apply the Style to two buttons, WPF tries to set the same TextBlock element as Content for the two buttons - this can't work. In WPF, for any element, you can only have one logical parent.
Update your style to the following, to get the desired behavior:
<Style x:Key="styleInfomationButton" TargetType="{x:Type Button}">
<Setter Property="Width" Value="22" />
<Setter Property="Height" Value="22" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Grid Width="20" Height="20">
<Ellipse Fill="#81A9F0" />
<<TextBlock FontWeight="ExtraBold" Foreground="White" HorizontalAlignment="Center" VerticalAlignment="Center">?</TextBlock>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Very good article on Understanding the Visual Tree and Logical Tree in WPF