for your ease you ca do this also..
private void slider1_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
if (slider1 == null || slider2 == null)
return;
if (slider1.Value >= slider2.Value)
{
slider2.Value = slider1.Value;
}
}
private void slider2_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
if (slider1 == null || slider2 == null)
return;
if (slider2.Value <= slider1.Value)
{
slider1.Value = slider2.Value;
}
}