最近在开发Windows 8 应用的时候碰到了一个莫名的问题，错误内容如下：（其中 **.DLL是本地创建的项目，在主项目中添加了引用，其中大部分代码是MVVM light 框架库的代码）
System.InvalidCastException”类型的异常在 **.DLL 中发生，但未在用户代码中进行处理
其他信息: Unable to cast COM object of type 'System.ComponentModel.PropertyChangedEventHandler' to class type 'System.ComponentModel.PropertyChangedEventHandler'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface.
前提是：在charm栏中选择分享，并选择分享到的应用；正常启动应用是不会有事的。（我很纳闷为什么，渴望大神赐教）
出错代码是这里（红色字体部分）：
[SuppressMessage("Microsoft.Design", "CA1030:UseEventsWhereAppropriate", Justification = "This cannot be an event")] protected virtual void RaisePropertyChanged(string propertyName) {#if WIN8 if (string.IsNullOrEmpty(propertyName)) { throw new NotSupportedException( "Raising the PropertyChanged event with an empty string or null is not supported in the Windows 8 developer preview"); } else {#endif //VerifyPropertyName(propertyName); var handler = PropertyChangedHandler; if (handler != null) { handler(this, new PropertyChangedEventArgs(propertyName)); }#if WIN8 }#endif }
我以为是框架本身的问题，于是在相应的代码中，自己重新实现INotifyPropertyChanged接口，并实现此接口：
public class LoginViewModel : ViewModelBase,INotifyPropertyChanged { event PropertyChangedEventHandler PropertyChanged; void NotifyPropertyChanged(string name) { if (PropertyChanged != null) PropertyChanged(this,new PropertyChangedEventArgs(name); } } 我差了相关帖子，看到了这个回复：
Just cast it to INotifyCollectionChanged
var collectionChanged = propertyObject as INotifyCollectionChanged;if (collectionChanged != null) collectionChanged.CollectionChanged += ... 于是我修改代码为如下：
public class LoginViewModel : ViewModelBase,INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; void NotifyPropertyChanged(string name) { var obj = this as INotifyPropertyChanged; if (obj != null) obj.PropertyChanged += (s, e) => { PropertyChanged(s, new PropertyChangedEventArgs(name)); }; } } OK，问题解决，关键是谁能告诉我这是为什么，什么情况下会出现这个错误，为什么会在分享中出现，而正常状态下不会呢？