How to get previous value from slider

I'm having problems on the toggle switch and the slider.

The value of the slider is used to increase or decrease the volume of my media element.

However, let's say if I set the value of the slider to '50' and I toggle the switch to 'off' my media element.

How do I capture the previous value from the slider when I toggle the switch back to 'on'?

At the moment, I set the value for slider to '100' when sw_music.IsOn

XAML:

    <Slider x:Name="slider" HorizontalAlignment="Left" VerticalAlignment="Top" Width="154" Margin="45,0,0,0" Height="42" Maximum="100" Value="100"/>    <ToggleSwitch x:Name="sw_music" Header="SOUND" IsOn="{Binding Value, ElementName=slider}"/>    <MediaElement x:Name="Intro_Sound" Source="SoundEffects/Intro.wav" Volume="{Binding Value, ElementName=slider}"/>

Code-Behind:

   

private void sw_music_Toggle(object sender, RoutedEventArgs e)    
{        
if(slider.Value >= 1)        
{            
    if (sw_music.IsOn)            
    {                
         slider.Value = 100;             Intro_Sound.Play();            
    }  else            
    {               
         slider.Value = 0;            Intro_Sound.Stop();   }          if(slider.Value > 1)       {                
         Intro_Sound.Play();          sw_music.IsOn = true;         }        
}    
}    

private void Slider_ValueChanged(object sender, RangeBaseValueChangedEventArgs e)        
{    Intro_Sound.Volume = (slider.Value) / 100;             
     if (slider.Value == 0)      {                sw_music.IsOn = false;        }          else       {              sw_music.IsOn = true;       }       
}