Let extension method

[Simplifier]

// Use .let and forget weird helper methods
val data = DataPoint(1, 22.1, DataPoint(2, 22.8))
val result = data.child?.child?.
            let { toFahrenheit(it.celsius) } ?: Double.MIN_VALUE

Let extension could be easily written in c# like this

static class Ext
{
    public static TR Let<T, TR>(this T obj, Func<T, TR> func) => func(obj);
}

And then c# example would be pretty similar to kotlin's

var data = new DataPoint(1, 22.1, new DataPoint(2, 22.8));
var result = data.Child?.Child?
    .Let(p => ToFahrenheit(p.Celsius)) ?? double.MinValue;