5.属性变化通知

属性变化通知
Prism框架提供了BindableBase类，用于做数据处理（例如属性的变化通知等）。

五种属性变化通知方式

通过继承BindableBase类，可以更加便捷地在WPF中实现属性变化通知，具体有如下五种方式。
其中前三种没啥特殊的，第四种方式可以在属性变化时，通知其他属性的绑定控件；而第五种方式则可以在属性发生变化后调用指定的函数。
测试后只有第二种和第三种能用，其他的都不能用，看了下BindableBase源码应该是底层缓存值和设置值对比的问题，还没输入研究

 

测试代码

public class MainViewModel : BindableBase
{
    private string _value;

    public string Value123
    {
        get => _value;
        set
        {
            _value = value;
            // 第一种方式【有问题】
            SetProperty(ref _value, value);

            // 第二种方式[没问题]
            //this.OnPropertyChanged(new System.ComponentModel.PropertyChangedEventArgs("Value123"));

            // 第三种方式[没问题]
            //this.RaisePropertyChanged();

            // 第四种方式：可以通知另一个属性【有问题】
            //SetProperty(ref _value, value, "Value1231");

            // 第五种方式【有问题】
            //SetProperty(ref _value, value, OnValueChanged);
            //————————————————
            //版权声明：本文为CSDN博主「SchuylerEX」的原创文章，遵循CC 4.0 BY - SA版权协议，转载请附上原文出处链接及本声明。
            //原文链接：https://blog.csdn.net/jjailsa/article/details/135708375
        }
    }
 
    private void OnValueChanged()
    {
        //属性成功变化后的执行函数
    }
}

UI代码

 

  <TextBox HorizontalAlignment="Left" Height="58" Margin="156,159,0,0" TextWrapping="Wrap" Text="{Binding Value123, UpdateSourceTrigger=PropertyChanged , Mode=TwoWay}" VerticalAlignment="Top" Width="133"/>
  <TextBox HorizontalAlignment="Left" Height="58" Margin="367,159,0,0" TextWrapping="Wrap" Text="{Binding Value123, UpdateSourceTrigger=PropertyChanged , Mode=TwoWay}" VerticalAlignment="Top" Width="229"/>

 

 

 

 

BindableBase的源码

/// <summary>
/// Implementation of <see cref="INotifyPropertyChanged"/> to simplify models.
/// </summary>
public abstract class BindableBase : INotifyPropertyChanged
{
    /// <summary>
    /// Occurs when a property value changes.
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    /// <summary>
    /// Checks if a property already matches a desired value. Sets the property and
    /// notifies listeners only when necessary.
    /// </summary>
    /// <typeparam name="T">Type of the property.</typeparam>
    /// <param name="storage">Reference to a property with both getter and setter.</param>
    /// <param name="value">Desired value for the property.</param>
    /// <param name="propertyName">Name of the property used to notify listeners. This
    /// value is optional and can be provided automatically when invoked from compilers that
    /// support CallerMemberName.</param>
    /// <returns>True if the value was changed, false if the existing value matched the
    /// desired value.</returns>
    protected virtual bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
    {
        if (EqualityComparer<T>.Default.Equals(storage, value)) return false;

        storage = value;
        RaisePropertyChanged(propertyName);

        return true;
    }

    /// <summary>
    /// Checks if a property already matches a desired value. Sets the property and
    /// notifies listeners only when necessary.
    /// </summary>
    /// <typeparam name="T">Type of the property.</typeparam>
    /// <param name="storage">Reference to a property with both getter and setter.</param>
    /// <param name="value">Desired value for the property.</param>
    /// <param name="propertyName">Name of the property used to notify listeners. This
    /// value is optional and can be provided automatically when invoked from compilers that
    /// support CallerMemberName.</param>
    /// <param name="onChanged">Action that is called after the property value has been changed.</param>
    /// <returns>True if the value was changed, false if the existing value matched the
    /// desired value.</returns>
    protected virtual bool SetProperty<T>(ref T storage, T value, Action onChanged, [CallerMemberName] string propertyName = null)
    {
        if (EqualityComparer<T>.Default.Equals(storage, value)) return false;

        storage = value;
        onChanged?.Invoke();
        RaisePropertyChanged(propertyName);

        return true;
    }

    /// <summary>
    /// Raises this object's PropertyChanged event.
    /// </summary>
    /// <param name="propertyName">Name of the property used to notify listeners. This
    /// value is optional and can be provided automatically when invoked from compilers
    /// that support <see cref="CallerMemberNameAttribute"/>.</param>
    protected void RaisePropertyChanged([CallerMemberName] string propertyName = null)
    {
        OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
    }

    /// <summary>
    /// Raises this object's PropertyChanged event.
    /// </summary>
    /// <param name="args">The PropertyChangedEventArgs</param>
    protected virtual void OnPropertyChanged(PropertyChangedEventArgs args)
    {
        PropertyChanged?.Invoke(this, args);
    }
}