Question

I have a ComboBox and a TextBox and want to enable/disable TextBox only, when first item is selected in ComboBox.

This code works: (disable when first item is selected)

            <ComboBox SelectedIndex="{Binding Mode}">
                <ComboBoxItem>Mode 1</ComboBoxItem>
                <ComboBoxItem>Mode 2</ComboBoxItem>
                <ComboBoxItem>Mode 3</ComboBoxItem>
            </ComboBox>
                <TextBox Text="{Binding ValueNotForMode1}">
                    <TextBox.Style>
                        <Style>
                            <Style.Triggers>
                                <DataTrigger Binding ="{Binding Mode}" Value="0">
                                    <Setter Property="TextBox.IsEnabled" Value="False"/>
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </TextBox.Style>
                </TextBox>

This one doesn’t work: (enable when first item is selected)

            <ComboBox SelectedIndex="{Binding Mode}">
                <ComboBoxItem>Mode 1</ComboBoxItem>
                <ComboBoxItem>Mode 2</ComboBoxItem>
                <ComboBoxItem>Mode 3</ComboBoxItem>
            </ComboBox>
                <TextBox IsEnabled="False" Text="{Binding ValueForMode1}">
                    <TextBox.Style>
                        <Style>
                            <Style.Triggers>
                                <DataTrigger Binding ="{Binding Mode}" Value="0">
                                    <Setter Property="TextBox.IsEnabled" Value="True"/>
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </TextBox.Style>
                </TextBox>

Isn’t it possible to enable a control via DataTrigger?

Or how can I tell the control, what to do, when the Trigger not occures?

Answer 1

Move IsEnabled="False" from your TextBox to your TextBox.Style.

<Setter Property="TextBox.IsEnabled" Value="False" />

See Dependency Property Value Precedence for clearer understanding.