c# – 该字段如何为空?
发布时间:2020-12-15 04:28:16 所属栏目:百科 来源:网络整理
导读: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 NotifyPropertyChangedT(ExpressionFuncT expression){ string propertyName = GetPropertyName(expression)
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. 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 [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 } (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |