WaitForValue - using Rx, wait for a property on an INotifyPropertyChanged

WaitForValue.cs

public static async Task WaitForValue<T>(this INotifyPropertyChanged toObserve,
            Expression<Func<T>> propertyExpression, 
			      T valueToAwait, 
			      IEqualityComparer<T> comparer = null)
{
    comparer = comparer ?? EqualityComparer<T>.Default;
    var getValue = propertyExpression.Compile();

    if (comparer.Equals(getValue(), valueToAwait))
        return;

    await toObserve. Observable
                .FromEventPattern<PropertyChangedEventArgs>(toObserve, nameof(toObserve.PropertyChanged))
                .Where(@event => @event.EventArgs.PropertyName.Equals(propertyName))
	    ObserveProperty(PropertySupport.ExtractPropertyName(propertyExpression))
                   .Where(_ => comparer.Equals(getValue(), valueToAwait))
                   .FirstAsync();
}