基于绑定对象和模型属性的可见绑定

Question

I ran in to the unique situation today where I needed to bind the Visible property of a button in a DataGridRow to be based on both a property of the bound object and of the model backing it.

XAML:

<t:DataGrid ItemsSource="{Binding Items}">
    <t:DataGrid.Columns>
        <t:DataGridTemplateColumn>
            <t:DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <Button Visibility="IsEditable OR IsAdmin"/>
                </DataTemplate>
            </t:DataGridTemplateColumn.CellTemplate>
        </t:DataGridTemplateColumn>
    </t:DataGrid.Columns>
</t:DataGrid>

Model:

class TheModel
{
    public ObservableCollection<Whatever> Items { get; set; }
    public bool IsAdmin { get; set; }
}

Class:

class Whatever
{
    public bool IsEditable { get; set; }
}

This stumped me. The only concept that I could think might work would be somehow passing the bound object and either the entire model or just the IsAdmin property to a static method on a converter or something. Any ideas?

Answer 1

Firstly, you cannot directly use a Boolean for Visibility. You need to use the BooleanToVisibilityConverter .

Secondly, about the OR , you have different options:

1. Create a readonly property IsEditableOrAdmin in Whatever which returns the value you want. Drawback: Your Whatever will need a back-reference to TheModel .

2. Use a MultiBinding and write an IMultiValueConverter . Then, pass both values in the MultiBinding. Since TheModel is no longer in the DataContext scope at that point, you could use the ElementName property of the Binding to refer to a UI element where TheModel is still accessible.

   Example (untested):

    <SomeElementOutsideYourDataGrid Tag="{Binding TheModel}" /> ... <Button> <Button.Visibility> <MultiBinding Converter="{StaticResource yourMultiValueConverter}"> <Binding Path="IsEditable" /> <Binding ElementName="SomeElementOutsideYourDataGrid" Path="Tag.IsAdmin"/> </MultiBinding> </Button.Visibility> </Button> 

3. Use a more powerful binding framework such as PyBinding .