Caliburn NotifyOfPropertyChange：System.InvalidCastException

Question

我们在我们的应用程序中使用了 caliburn 框架。

我的视图模型中有一个属性，当它的值发生变化时，它应该为另一个属性调用一个 NotifyOfPropertyChanged。

我认为我可以按如下方式做到这一点：

    public AnalogSensorState State
    {
        get
        {
            if (LowerErrorLevelExceeded)
            {
                return AnalogSensorState.LowerErrorExceeded;
            }
            if (LowerWarningLevelExceeded)
            {
                return AnalogSensorState.LowerWarningExceeded;
            }
            if (UpperErrorLevelExceeded)
            {
                return AnalogSensorState.UpperErrorExceeded;
            }
            if (UpperWarningLevelExceeded)
            {
                return AnalogSensorState.UpperWarningExceeded;
            }
            return AnalogSensorState.Ok;
        }
    }

    public bool LowerErrorLevelExceeded
    {
        get => _lowerErrorLevelExceeded;
        set
        {
            Set(ref _lowerErrorLevelExceeded, value, nameof(LowerErrorLevelExceeded));
            NotifyOfPropertyChange(() => nameof(State));
        }
    }
    ...

当执行布尔值 setter 时，我在 NotifyOfPropertyChange 调用中得到一个无效的转换异常。

为什么？

异常：

System.InvalidCastException: 'Unable to cast object of type 'System.Linq.Expressions.ConstantExpression' to type 'System.Linq.Expressions.MemberExpression'.'

Answer 1

根据 Caliburn.Micro 中的 PropertyChangedBase class，您应该使用 NotifyOfPropertyChange(nameof(State)); 或 NotifyOfPropertyChange(() => State);。它接受名称为属性或名称为 Expression<Func<TProperty>> 的字符串属性

    /// <summary>Notifies subscribers of the property change.</summary>
    /// <param name="propertyName">Name of the property.</param>
    public virtual void NotifyOfPropertyChange([CallerMemberName] string propertyName = null)
    {
      if (!this.IsNotifying || this.PropertyChanged == null)
        return;
      this.OnUIThread((Action) (() => this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName))));
    }

    public void NotifyOfPropertyChange<TProperty>(Expression<Func<TProperty>> property)
    {
      this.NotifyOfPropertyChange(property.GetMemberInfo().Name);
    }

Caliburn NotifyOfPropertyChange：System.InvalidCastException

Caliburn NotifyOfPropertyChanged : System.InvalidCastException

c#

wpf

mvvm

caliburn.micro