WPF：更改所有数据绑定的路径

Question

I am trying to change all the databindings in a window when a user clicks on a button. Note: the following code is pseudo.

Assuming we have a class called sensor:

public class Sensor : INotifyPropertyChanged {
  public int HighVal {get; set;}
  public int LowVal {get; set;}
}

And the following model to which we bind:

public class SomeModel {
  public Sensor MovementSensor {get; set;}
  public Sensor TemperatureSensor {get; set;}
  public Sensor BarometerSensor {get; set;}
}

In my xaml, I would like to bind in the following way:

<TextBox Text="{Binding MyModel.MovementSensor.HighVal}"/>
<TextBlock Text="{Binding MyModel.BarometerSensor.HighVal}"/>

I would like to have a button (or something similar) that upon clicking, will change all databindings' path from HighVal to LowVal, eg

<TextBox Text="{Binding MyModel.MovementSensor.LowVal}"/>
<TextBlock Text="{Binding MyModel.BarometerSensor.LowVal}"/>

Is there an elegant way to perform this without iterating over all databindings in the window?

Thanks!

Answer 1

You could use a MultiBinding that is connected with the two values of the sensor and a third property to determine the current value:

<TextBlock>
    <TextBlock.Resources>
        <y:SensorValueConverter x:Key="SVC"></y:SensorValueConverter>
    </TextBlock.Resources>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource SVC}">            
            <Binding Path="MyModel.BarometerSensor.HighVal" />
            <Binding Path="MyModel.BarometerSensor.LowVal" />
            <Binding Path="MyModel.BarometerSensor.SelectedVal" />    
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

In the Windows tag you specify the namespace of the converter, but you have to replace the "YOUR-PROJECTNAME" placeholder:

<Window x:Class="..."
        ...
        xmlns:y="clr-namespace:YOUR-PROJECTNAME">

I have extended the class Sensor by the property SelectedVal which stores the value that should be shown in the TextBox. Changing it to "High" or to "Low" will immediatly update the Binding of the TextBox.

public enum SelectedValue
{
    High,
    Low
}

public class Sensor : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;       

    public int HighVal {get; set;}
    public int LowVal {get; set;}

    SelectedValue selval = SelectedValue.High;
    public SelectedValue SelectedVal
    {
        get
        {
            return selval;
        }
        set
        {
            selval = value;
            PropertyChanged(this, new PropertyChangedEventArgs("SelectedVal"));
        }
    }
}

And now the most important part, the ValueConverter for the Binding that will choose the right value depending on the state of SelectedVal (class CultureInfo is the System.Globalization namespace):

public class SensorValueConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {         
        SelectedValue val = (SelectedValue)values[2];

        if (val == SelectedValue.High)
        {
            return values[0].ToString();
        }
        else
        {
            return values[1].ToString();
        }
    }

    public object[] ConvertBack(object value, Type[] targetType, object parameter, CultureInfo culture)
    {

        throw new NotImplementedException();

    }
}

To change the selected value of the sensor, you need to modify the SelectedVal property:

MyModel.BarometerSensor.SelectedVal = SelectedValue.Low

UPDATE:
To assign the binding to many Elements, a style can be defined in a separate file (Styles.xaml):

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:y="clr-namespace:YOUR-PROJECTNAME">

    <y:SensorValueConverter x:Key="SVC"></y:SensorValueConverter>
    <Style x:Key="ValStyle" TargetType="TextBlock">
        <Setter Property="Text">
            <Setter.Value>
                <MultiBinding Converter="{StaticResource SVC}">
                    <Binding Path="MyModel.BarometerSensor.HighVal" />
                    <Binding Path="MyModel.BarometerSensor.LowVal" />
                    <Binding Path="MyModel.BarometerSensor.SelectedVal" />
                </MultiBinding>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

To use this Style from other windows put simply this line in the resources of the window:

<ResourceDictionary Source="Styles.xaml"></ResourceDictionary>

Finally you need to assign the created style to all TextBlocks that should display the values:

<TextBlock Style="{StaticResource ValStyle}"></TextBlock>

For a sensor with only one property, you can create another style in Styles.xaml that has to be bound to only one property:

<Style x:Key="SpecialValStyle" TargetType="TextBlock">
    <Setter Property="Text">            
        <Binding Path="MyModel.BarometerSensor.HighVal" />
    </Setter>
</Style>