C# Safe navigation operator - what is actually going on?

Let's walk through this logically.

var f = ???;
var i = f?.Measure;
var t = i.HasValue;

We don't know if f is null or not.

Therefore, i is defined as int?, and t is a bool

Now, let's walk through this:

var f = ???;
var i = f?.Measure.HasValue;

If f is null, then the result (i) is null
If f is not null, then the result (i) is Measure.HasValue, which is a bool.

Therefore, i is a bool?.

If f is null, we short-circuit and return null. If it's not, we return the bool result of .HasValue.

Essentially, when using ?. - the return type must be a reference value, or a Nullable<T>, as the expression can short circuit to return null.

Related