升级后，Monotouch在单击按钮时崩溃

Question

I have upgraded to MonoTouch 5. Ever since the upgrade none of my newly created buttons work in my existing projects. All the buttons created and bound to events before the upgrade still work perfectly but as soon as I create a new button and bind it to an event, the app crashes in the simulator.

The interesting part is that when I create a new project after the upgrade, and create a button in interface builder as I usually did it and bind it to an event as I usually did, it works fine. The crash only happens when I add a new button after the upgrade to an existing project that was created before the upgrade. The buttons created and bound after the upgrade is done exactly the same as those done before the upgrade.

I have also created new test projects after the upgrade and compared the code in the AppDelegate and Main cs files. Everything is exactly the same!

Is there something I might be missing? I have scouted the internet and tried solutions from everywhere including Stack Overflow but to no avail. I do not really want to move the existing code to new projects as it is a lot of work.

Stack Trace Error:

012-07-03 19:18:30.189 Calculator[605:1207] -[__NSCFType btnSave:]: unrecognized selector sent to instance 0x7106fd0

Unhandled Exception: MonoTouch.Foundation.MonoTouchException: Objective-C exception thrown.  Name: NSInvalidArgumentException Reason: -[__NSCFType btnSave:]: unrecognized selector sent to instance 0x7106fd0
  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00042] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:29 
  at ScamCalculator.Application.Main (System.String[] args) [0x00000] in /Users/joachimpr/Projects/ScamCalculator/ScamCalculator/Main.cs:17 
[ERROR] FATAL UNHANDLED EXCEPTION: MonoTouch.Foundation.MonoTouchException: Objective-C exception thrown.  Name: NSInvalidArgumentException Reason: -[__NSCFType btnSave:]: unrecognized selector sent to instance 0x7106fd0
  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00042] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:29 
  at ScamCalculator.Application.Main (System.String[] args) [0x00000] in /Users/joachimpr/Projects/ScamCalculator/ScamCalculator/Main.cs:17 

The button is linked up as an outlet in Interface Builder. The button event code:

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

            // Perform any additional setup after loading the view, typically from a nib.

            btnSave.TouchUpInside += (sender, e) => {
                Console.WriteLine("click");
            };
        }

Answer 1

Turns out there was a view that was losing its instance. I moved this view to a class instance and now it works fine.