WPF - Converting to multiple properties possible?

Question

I have a textbox and a checkbox, i would like to set three properties on the textbox based on whether the checkbox is checked or not.

I can bind the properties to the checkbox but then i need to know what property is being bound in the converter.

For example, when unchecked i would like the textbox properties to be AcceptsReturn="False" TextWrapping="NoWrap" Height="25".

Then checked: AcceptsReturn="True" TextWrapping="Wrap" Height="100".

Will this require 3 converters or can i tell the converter "if checked==true && boundfrom == height, return 100"

Thanks, Kohan

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Accepted Solution

<TextBox Name="txtAnswer" Margin="5" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Hidden" >
                <TextBox.Style>
                    <Style>
                        <Style.Triggers>
                            <DataTrigger Binding="{Binding ElementName=cbMultiLine, Path=IsChecked}" Value="True">
                                <Setter Property="TextBox.TextWrapping" Value="Wrap" />
                                <Setter Property="TextBox.Height" Value="100" />
                                <Setter Property="TextBox.AcceptsReturn" Value="True" />
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </TextBox.Style>
            </TextBox>

Answer 1

<CheckBox x:Name="myCheckBox" />
<TextBox 
    AcceptsReturn="{Binding ElementName=myCheckBox, Path=IsChecked}"
    TextWrapping="{Binding ElementName=myCheckBox, Path=IsChecked, Converter={StaticResource boolToTextWrappingConverter}}" 
    Height="{Binding ElementName=myCheckBox, Path=IsChecked, Converter={StaticResource boolToHeightConverter}}" 
/>

this would reduce it to 2 converters. you could also write one boolToTextWrappingOrHeight converter as you suggested in your post, and pass in a CommandParameter=height and CommandParameter=textwrapping and look at the parameter in the converter, but I'm not a fan of that approach. A third option would be to create IsChecked, TextWrapping and Height properties in your viewmodel, bind to those, and put your conversion logic in the properties.

Answer 2

This should work with one converter by using the ConverterParameter property on the binding:

Converter="{StaticResource MyIsCheckedConverter}" ConverterParameter="height"

The Converter would look like:

public class IsCheckedConverter : IValueConverter
{
    public object Convert(
     object value, Type targetType,
     object parameter, System.Globalization.CultureInfo culture)
    {
        object returnValue;

        if (!((bool?)value).HasValue)
            //do something if null (but I don't see why it would be)

        switch ((string) parameter)
        {
            case "height":
                  returnValue = ((bool?)value).Value ? 100 : 25; 
                  break;
            case "TextWrapping":
                   .....
                  ..... 
        }

        return returnValue;
    }

    public object ConvertBack(
     object value, Type targetType,
     object parameter, System.Globalization.CultureInfo culture)
    {
        //Likewise for convert back but I think in your case you wouldn't need to convert back
    }
}

Answer 3

i would seriously consider using a data trigger. its a ui concern so i would try to avoid using your view model. you could do this with just a few lines of xaml.