TraverseWithStructs.cs

// use with LINQPad

void Main()
{
	var f = new Foo();
	
	var n1 = Traverse.Create(f).Field("bar").Field("n").GetValue<int>();
	Console.WriteLine($"n1={n1}");
	
	// does not work because `Field("bar") returns a copy of the struct
	Traverse.Create(f).Field("bar").Field("n").SetValue(456);
	//
	var n2 = Traverse.Create(f).Field("bar").Field("n").GetValue<int>();
	Console.WriteLine($"n2={n2}");

	// works because it gets a copy of the struct, updates it and writes it back
	var bar =  Traverse.Create(f).Field("bar");
	var b = bar.GetValue();
	Traverse.Create(b).Field("n").SetValue(789);
	bar.SetValue(b);

	var n3 = Traverse.Create(f).Field("bar").Field("n").GetValue<int>();
	Console.WriteLine($"n3={n3}");
}

public class Foo
{
	private struct Bar
	{
		int n;

		public Bar(int n)
		{
			this.n = n;
		}
	}

	private Bar bar;
	
	public Foo()
	{
		bar = new Bar(123);
	}
}