C# 7 - Return reference - https://codingblast.com/csharp-7-return-reference-local-reference/

LocalReference.cs

public class RefLocals
{
    private int _age = 15;
    
    private int[] _numbers = { 3, 2, 5, 4 };

    public void ReferenceToField()
    {
        ref int someReferenceToAge = ref _age;

        someReferenceToAge = 45;
        
        ref int secondElement = ref _numbers[1];

        secondElement = 33;
    }

    public void PrintAge()
    {
        Console.WriteLine($"Age: {_age}");
    }
}