C# WPF中依赖值FeesAmount不更新问题求助

场景与代码 #

XAML布局 #

<StackPanel>
    <Label>Fee Percentage:</Label>
    <TextBox Text="{Binding ContractExtension.FeesPercentage, UpdateSourceTrigger=PropertyChanged}"></TextBox>
</StackPanel>
<StackPanel>
    <Label>Amount in $</Label>
    <TextBox Text="{Binding FeesAmount, Mode=OneWay}" IsReadOnly="True"></TextBox>
</StackPanel>

MainViewModel代码 #

public class MainViewModel : BaseViewModel
{
    private ContractExtension contractExtension;

    public ContractExtension ContractExtension
    {
        get { return contractExtension; }
        set
        {
            contractExtension = value;
            OnPropertyChanged(nameof(ContractExtension));
            OnPropertyChanged(nameof(FeesAmount));
        }
    }

    public decimal FeesAmount
    {
        get
        {
            decimal feesAmount = Toolbox.GetContractGivenValue(contract, false) * ContractExtension.FeesPercentage / 100;
            return feesAmount;
        }
    }
}

BaseViewModel代码 #

public abstract class BaseViewModel : INotifyPropertyChanged
{
    #region Attributes
    private Window parentWindow;
    #endregion Attributes

    #region Properties
    public Window ParentWindow
    {
        get
        {
            return parentWindow;
        }
        set
        {
            parentWindow = value;
            SetParentWindow(value);
        }
    }

    public abstract void SetParentWindow(Window parentWindow);
    public SearchBoxViewModel SearchBoxViewModel { get; }
    #endregion Properties

    public event PropertyChangedEventHandler? PropertyChanged;

    public abstract void ResetData();

    protected static ExceptionManager exceptionManager;

    public BaseViewModel()
    {
        exceptionManager = new ExceptionManager();
        SearchBoxViewModel = new SearchBoxViewModel();
    }

    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public void RefreshProperty(string propertyName)
    {
        OnPropertyChanged(propertyName);
    }
}

问题现象 #

修改第一个文本框的FeesPercentage值时，第二个文本框的FeesAmount未同步更新。调试发现：初始化时会进入ContractExtension的setter，但编辑FeesPercentage时不会触发该setter，因此无法执行OnPropertyChanged(nameof(FeesAmount))。

已排查内容 #

• 确认ContractExtension实现了INotifyPropertyChanged
• 验证DataContext设置正确
• 确认FeesPercentage变化时会触发自身的setter

解决方案 #

当前代码仅在替换整个ContractExtension对象时才会触发FeesAmount的PropertyChanged，但编辑FeesPercentage是修改ContractExtension内部属性，对象引用未变，所以MainViewModel的ContractExtension setter不会被调用。需要监听ContractExtension的PropertyChanged事件，在FeesPercentage变化时主动刷新FeesAmount。

修改MainViewModel #

private ContractExtension contractExtension;

public ContractExtension ContractExtension
{
    get { return contractExtension; }
    set
    {
        // 移除旧对象的事件监听
        if (contractExtension != null)
        {
            contractExtension.PropertyChanged -= ContractExtension_PropertyChanged;
        }
        contractExtension = value;
        // 添加新对象的事件监听
        if (contractExtension != null)
        {
            contractExtension.PropertyChanged += ContractExtension_PropertyChanged;
        }
        OnPropertyChanged(nameof(ContractExtension));
        OnPropertyChanged(nameof(FeesAmount));
    }
}

private void ContractExtension_PropertyChanged(object? sender, PropertyChangedEventArgs e)
{
    // 当FeesPercentage属性变化时，触发FeesAmount的更新
    if (e.PropertyName == nameof(ContractExtension.FeesPercentage))
    {
        OnPropertyChanged(nameof(FeesAmount));
    }
}

确保ContractExtension的FeesPercentage正确触发事件 #

确认ContractExtension中FeesPercentage的setter正确触发PropertyChanged：

// ContractExtension中的示例实现
private decimal feesPercentage;
public decimal FeesPercentage
{
    get => feesPercentage;
    set
    {
        if (feesPercentage != value)
        {
            feesPercentage = value;
            OnPropertyChanged(nameof(FeesPercentage));
        }
    }
}

补充说明 #

若其他模块用相同方式正常工作，大概率是那些模块中存在替换整个对象的操作，或已隐式处理了子对象的PropertyChanged监听。

内容的提问来源于stack exchange，提问作者Elzardi