我得到一个空的异常,但该字段已初始化为空列表.那么怎么可能是null？
该方法的第二行发生错误(在_hydratedProperties上)：
protected virtual void NotifyPropertyChanged<T>(Expression<Func<T>> expression)
{
string propertyName = GetPropertyName(expression);
if (!this._hydratedProperties.Contains(propertyName)) { this._hydratedProperties.Add(propertyName); }
}
这就是这个领域如何被宣布：
public abstract class EntityBase<TSubclass> : INotifyPropertyChanged where TSubclass : class
{
private List<string> _hydratedProperties = new List<string>();
这是它的设置：
public Eta Eta
{
get { return this._eta; }
set
{
this._eta = value;
NotifyPropertyChanged(() => this.Eta);
}
}
这是完整的课程(删除了注释和非相关部分)：
[DataContract]
public abstract class EntityBase<TSubclass> : INotifyPropertyChanged where TSubclass : class
{
private List<string> _hydratedProperties = new List<string>();
public bool IsPropertyHydrated(string propertyName)
{
return this._hydratedProperties.Contains(propertyName);
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void NotifyPropertyChanged<T>(Expression<Func<T>> expression)
{
string propertyName = GetPropertyName(expression);
if (!this._hydratedProperties.Contains(propertyName)) { this._hydratedProperties.Add(propertyName); }
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this,new PropertyChangedEventArgs(propertyName));
}
}
public string GetPropertyName<T>(Expression<Func<T>> expression)
{
MemberExpression memberExpression = (MemberExpression)expression.Body;
return memberExpression.Member.Name;
}
}
派生类：
[DataContract]
public class Bin : EntityBase<Bin>
{
private Eta _eta;
[DataMember]
public Eta Eta
{
get { return this._eta; }
set
{
this._eta = value;
NotifyPropertyChanged(() => this.Eta);
}
}
}
解决方法
以下是线索：
[DataContract]
对. DataContractSerializer does not call any constructor.相反,它使用FormatterServices.GetUninitializedObject来创建将被反序列化的对象.这将绕过构造函数调用.
您的初始化程序：
private List<string> _hydratedProperties = new List<string>();
被编译器转换为隐式的默认构造函数.
作为解决方法,您可以使用a deserialization callback with OnDeserializingAttribute：
[DataContract]
public abstract class EntityBase<TSubclass> : INotifyPropertyChanged
where TSubclass : class
{
private List<string> _hydratedProperties;
protected EntityBase()
{
Init();
}
private void Init()
{
_hydratedProperties = new List<string>()
}
[OnDeserializing]
private void OnDeserializing(StreamingContext context)
{
Init();
}
// ... rest of code here
}
