C# 升级后单击按钮时Monotouch崩溃

我已经升级到MonoTouch 5。自从升级以来，我新创建的按钮在现有项目中都不起作用。升级前创建并绑定到事件的所有按钮仍然可以正常工作，但只要我创建一个新按钮并将其绑定到事件，应用程序就会在模拟器中崩溃

有趣的是，当我在升级后创建一个新项目，像往常一样在interface builder中创建一个按钮，并像往常一样将其绑定到事件时，它工作得很好。只有在升级后向升级前创建的现有项目添加新按钮时，才会发生崩溃。升级后创建和绑定的按钮与升级前创建和绑定的按钮完全相同

升级后，我还创建了新的测试项目，并比较了AppDelegate和主cs文件中的代码。一切都一模一样

有什么我可能遗漏的吗？我搜索过互联网，尝试过各种解决方案，包括堆栈溢出，但都没有用。我真的不想将现有的代码转移到新项目中，因为这是一项大量的工作

堆栈跟踪错误：

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 

该按钮在Interface Builder中链接为插座。按钮事件代码：

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");
            };
        }

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原来有一个视图正在丢失其实例。我将此视图移动到一个类实例，现在它工作正常