Change a source of image in a controltemplate

Hi everyone,

I'm starting with Xamarin and I didn't find how to change a source of image in controltemplate. I want to change the image when the Wi-Fi state change.
I didn't use the MVVM model.
I attach my code of my controltemplate in App.xaml.

<ControlTemplate x:Key="State"> <Grid ColumnSpacing="0"> <Grid.ColumnDefinitions> <ColumnDefinition Width="*"/> <ColumnDefinition Width="11*"/> </Grid.ColumnDefinitions>

                <BoxView Grid.Column="0" Style="{DynamicResource boxviewStyle}"/>
                <ContentPresenter Grid.Column="1" />

                <Grid Grid.Column="0">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="*"/>
                    </Grid.RowDefinitions>

                    <Button x:Name="ButtonHome" Grid.Column="0" Grid.Row="0" Style="{DynamicResource buttonStyle}" Image="home_48x46.png" Clicked="onClickedButtonHome"/>
                    <Label x:Name="LabelBattery" Grid.Column="0" Grid.Row="1" Style="{DynamicResource labelStyle}" TextColor="White" Text="100 %" VerticalOptions="Center" HorizontalOptions="Start" Margin="5"/>
                    <Image x:Name="Battery" Grid.Column="0" Grid.Row="1" Source="battery_icon_100_40px.png" VerticalOptions="Center" HorizontalOptions="End" Margin="5"/>
                    <Label x:Name="LabelTime" Grid.Column="0" Grid.Row="2" Style="{DynamicResource labelStyle}" HorizontalOptions="Center" Text="08:35"/>
                    <Button x:Name="ButtonGPS" Grid.Column="0" Grid.Row="3" Style="{DynamicResource buttonStyle}" Image="gps_icon_pos_70px.png" Clicked="onClickedButtonGPS"/>
                    <Image x:Name="ImageWIFI" Grid.Column="0" Grid.Row="4" Source="wifi_off_70px.png" HorizontalOptions="Center"/>
                    <Button x:Name="ButtonMore" Grid.Column="0" Grid.Row="6" Style="{DynamicResource buttonStyle}" Image="trois_points_70px.png" Clicked="onClickedButtonMore"/>
                </Grid>
            </Grid>
        </ControlTemplate>`

Thank you very much,