I am trying to use a multi-binding inside of a BindableLayout and I can't get the "Answer" binding to scope correctly.

This line: <Binding Path="SelectedAnswers" Source="{x:Reference this}" /> is working correctly and is passed into the converter.

This line: <Binding Path="Answer" Source="{RelativeSource Mode=Self}" /> is just null;

You can see on the Button text property I am using "Answer" there too and it is not null.

<FlexLayout Wrap="Wrap" BindableLayout.ItemsSource="{Binding CurrentQuestion.SurveyQuestionAnswers}">
        <BindableLayout.ItemTemplate>
            <DataTemplate x:DataType="viewmodels:SurveyQuestionAnswerViewModelRead">
                <StackLayout>
                    <Button Text="{Binding Answer}" Command="{Binding QuestionAnsweredCommand, Source={x:Reference this}}" CommandParameter="{Binding .}" >
    
                        <Button.IsVisible>
                            <MultiBinding Converter="{StaticResource ListAnyMultiValueConverter}">
                                <Binding Path="SelectedAnswers" Source="{x:Reference this}" />
                                <Binding Path="Answer" Source="{RelativeSource Mode=Self}" />
    
                            </MultiBinding>
                        </Button.IsVisible>
                    </Button>
                </StackLayout>
    
            </DataTemplate>
        </BindableLayout.ItemTemplate>
    </FlexLayout>

CodePudding user response：

The problem is a misunderstanding of {RelativeSource Mode=Self}. That is looking for a property Answer on the Button element. There is no such property of course.

(You could use this mode to refer to Text property of button. But might as well bind directly to the same variable that Text does.)

Do:
<Binding Path="Answer"/>

That will look in the BindingContext, just like {Binding Answer} did on Button Text.