Xamarin UINavigationController.ViewDidLoad running before constructor

CustomUiNavigationController.cs

using System.Text;
using MonoTouch.UIKit;

namespace App2
{
    public class CustomUiNavigationController : UINavigationController
    {
        private readonly StringBuilder _sb;

        public CustomUiNavigationController(UIViewController uiViewController)
            : base(uiViewController)
        {
            _sb = new StringBuilder();
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();

            _sb.Append("value"); //// null reference
        }
    }
}

I think I finally understand why I'm seeing this behavior: constructor is running first as one would expect, but the call to base constructor will cause ViewDidLoad to run before the full constructor ends (so in the example above, _sb hasn't been initialized yet!)

Confirmed by looking at call stack: the call order is base ctor -> ViewDidLoad -> local ctor.

I see that the expected .NET behavior for constructors is correct (sorry about that!), but in fairness doesn't make much sense to me to see the ViewDidLoad running from base ctor!