Could we have property of nullable struct return ref

[Thaina]

If it not be breaking change I wish Value property of nullable struct should return reference. But if it is I think we should have another property that would return reference of the struct in the nullable directly

Something like

Vector3? v = GetNullablePosition(name);
ref Vector3 rv = v.Reference; // throw error for null, like .Value

Console.WriteLine(v?.X); // 0.0f
rv.X += 10;
Console.WriteLine(v?.X); // 10.0f

[yaakov-h]

Shouldn't this be a dotnet/corefx or dotnet/standard issue?

[benaadams]

I assume is currently a language issue as you can't have null refs set by C# #497

[yaakov-h]

You wouldn’t need to, if it threw an exception as described when HasValue is false.

[svick]

I don't think such Reference property would be allowed under current ref returns rules. Specifically, ref-returning methods in structs are not allowed to return this or their own instance fields.

For example, this code:

struct MyNullable<T>
{
	T value;

	ref T Reference => ref value;
}

produces:

error CS8170: Struct members cannot return 'this' or other instance members by reference

[sharwell]

StrongBox<T> and ValueTuple<T> solved this by using public fields instead of properties.

[yaakov-h]

Although if you used a field here then you can’t throw an exception if it’s null.

[Thaina]

@svick Thanks. This is very sad. There are many existing function return nullable struct or logic using array of nullable and it has no easy way to edit internal value without copy

[Thaina]

@sharwell StrongBox<T> is class so it need to instantiate and defeat the purpose of being struct

ValueTuple<T> (bool,T) is more likely but it can't use ?? or ?. or protect the value from accessing when it being null