WPF - Radio button control template binding "IsChecked" not working - wpf

Question

I have a control template like below, and I want to get IsChecked property when user selects a radio button.
But when user select radio button "A" it's IsChecked property still show false. Why?
<ControlTemplate x:Key="RadioBtnTemplate" TargetType="{x:Type RadioButton}">
<Grid>
<StackPanel Margin="5">
<RadioButton Name="tempbtn" IsChecked="{TemplateBinding IsChecked}" FontFamily="Segoe UI" FontSize="18.667" Content="{TemplateBinding Content}" GroupName="{TemplateBinding GroupName}"/>
</StackPanel>
</Grid>
</ControlTemplate>
and I use this template:
<RadioButton GroupName="CG" x:Name="_rdoBtnA" Content="A" Template="{DynamicResource RadioBtnTemplate}" IsChecked="True"/>
<RadioButton GroupName="CG" x:Name="_rdoBtnB" Content="B" Template="{DynamicResource RadioBtnTemplate}" />
<RadioButton GroupName="CG" x:Name="_rdoBtnC" Content="C" Template="{DynamicResource RadioBtnTemplate}" />

Answer 1

If we take your example as is then you have two problems which cause the problems you are seeing.
Issue 1:
Firstly your design has created six not three <RadioButton> controls. The three in the <StackPanel> and then three that are created as part of the control template. All six radio buttons are now linked as part of the GroupName="CG" group.
As you know because they all belong to the same CG group only one of the six radio buttons can have the IsChecked property set to True. The three named controls _rdoBtnA, _rdoBtnB and _rdoBtnC are not even visible on the screen so they can never be set to True (and in the case of _rdoBtnA is promptly set to False from the XAML declared True the moment the template control is bound).
To resolve this situation, remove the GroupName="{TemplateBinding GroupName}" from the control template definition leaving only the three top level radio buttons in the group.
Issue 2: This is the issue I thought was the root of your problem to begin with. IsChecked={TemplateBinding IsChecked} is only OneWay binding and will not update the other way. To make the binding TwoWay you need to use the long-hand version of the binding definition, IsChecked="{Binding IsChecked, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"
The control template now becomes this by making those two changes.
<ControlTemplate x:Key="RadioBtnTemplate" TargetType="{x:Type RadioButton}">
<Grid>
<StackPanel Margin="5">
<RadioButton Name="tempbtn" IsChecked="{Binding IsChecked, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}" FontFamily="Segoe UI" FontSize="18.667" Content="{TemplateBinding Content}" />
</StackPanel>
</Grid>
</ControlTemplate>

Answer 2

you can use it this way:
<StackPanel Orientation="Horizontal">
<StackPanel.Resources>
<ControlTemplate x:Key="ButtonAsSwatchTemplate">
<Border x:Name="SwatchBorder" BorderThickness="1">
<Rectangle Fill="{TemplateBinding Property=Background}" Width="15" Height="15" />
</Border>
<ControlTemplate.Triggers>
<Trigger Property="ToggleButton.IsChecked" Value="True">
<Setter TargetName="SwatchBorder" Property="BorderBrush" Value="Yellow" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</StackPanel.Resources>
<RadioButton Template="{StaticResource ButtonAsSwatchTemplate}"
GroupName="CropGuidesColourRadioButtonGroup"
IsChecked="{Binding Checked}" Margin="2" Background="Red" />
<RadioButton Template="{StaticResource ButtonAsSwatchTemplate}"
GroupName="CropGuidesColourRadioButtonGroup"
IsChecked="{Binding Checked}" Margin="2" Background="Black" />
</StackPanel>
taken from StackOverFlow