MvvmLight中，两个依赖属性的值发生变化时影响第三个控件属性的用法

1. 使用数据绑定配合IValueConverter(值转换器)

创建一个自定义转换器，该转换器接收两个输入值，并根据他们是否相等返回相应的输出值。然后将这个转换器应用到第三个控件的属性上

public class EqualityToTextConverter : IValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        string value1 = (string)values[0];
        string value2 = (string)values[1];

        return value1 == value2 ? "Equal" : "Not Equal"; // 根据需要返回不同的文本
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException("EqualityToTextConverter只支持单向转换");
    }
}

在XAML中使用MultiBinding：

<Window.Resources>
    <local:EqualityToTextConverter x:Key="EqualityConverter"/>
</Window.Resources>

<!-- 假设这两个依赖属性都在同一个ViewModel中 -->
<Grid DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <TextBox Text="{Binding Property1}" />
    <TextBox Text="{Binding Property2}" />

    <!-- 第三个TextBox -->
    <TextBox>
        <TextBox.Text>
            <MultiBinding Converter="{StaticResource EqualityConverter}">
                <Binding Path="Property1" />
                <Binding Path="Property2" />
            </MultiBinding>
        </TextBox.Text>
    </TextBox>
</Grid>

 

使用命令或事件触发逻辑： 在ViewModel中创建一个命令，当两个属性值改变时执行此命令，命令内部比较两个属性并更新第三个TextBox的Text属性。

public class MyViewModel : ViewModelBase
{
    private string property1;
    public string Property1
    {
        get { return property1; }
        set
        {
            if (property1 != value)
            {
                property1 = value;
                RaisePropertyChanged(nameof(Property1));
                CheckEquality();
            }
        }
    }

    private string property2;
    public string Property2
    {
        get { return property2; }
        set
        {
            if (property2 != value)
            {
                property2 = value;
                RaisePropertyChanged(nameof(Property2));
                CheckEquality();
            }
        }
    }

    private void CheckEquality()
    {
        if (Property1 != Property2)
        {
            ThirdProperty = "Not Equal";
        }
        else
        {
            ThirdProperty = "Equal";
        }
    }

    private string thirdProperty;
    public string ThirdProperty
    {
        get { return thirdProperty; }
        set
        {
            if (thirdProperty != value)
            {
                thirdProperty = value;
                RaisePropertyChanged(nameof(ThirdProperty));
            }
        }
    }
}

<!-- XAML -->
<TextBox Text="{Binding Property1}" />
<TextBox Text="{Binding Property2}" />
<TextBox Text="{Binding ThirdProperty}" />