how to disable a navigation bar button item in iOS

Question

I have created a navigation controller. In the second view (which is pushed), I have some webservice call and placing a overlay view and setting

self.view.use

Answer 1

var menuBtn = new UIButton(UIButtonType.Custom);
menuBtn.Frame = new CGRect(x: 0.0, y: 0.0, width: 20, height: 20);
menuBtn.SetImage(new UIImage("filter"), UIControlState.Normal);

menuBtn.Alpha = 0.05f;   //to set the Alpha

menuBtn.Enabled = false;

tested on Mvvmcross Xamarin.iOS only