Null is considered empty string in style for TextBox WPF.

See more:

C#

.NET

WPF

This is my style code.

<Style x:Key="RequiredTextBoxForMultiple" TargetType="{x:Type TextBox}" BasedOn="{StaticResource {x:Type TextBox}}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type TextBox}">
                            <Grid>
                                <ScrollViewer SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" x:Name="PART_ContentHost"/>
                                <TextBlock x:Name="reqText" Text="<multiple>" removed="Pink" Opacity="0.5" Visibility="Hidden" FontStyle="Italic"></TextBlock>
                            </Grid>
                            <ControlTemplate.Triggers>
                                <MultiTrigger>
                                    <MultiTrigger.Conditions>
                                        <Condition Property="IsFocused" Value="False" />
                                        <Condition Property="Text"  Value="{x:Null}" />
                                    </MultiTrigger.Conditions>
                                    <Setter Property="Visibility" TargetName="reqText" Value="Visible" />
                                </MultiTrigger>
                            </ControlTemplate.Triggers>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

& this is my textbox.

<TextBox x:Name="txtBoxCustomTitle" 
 Style="{StaticResource RequiredTextBoxForMultiple}"
 Grid.Column="4" Grid.Row="2"
 Margin="17,3,0,0"
 Text="{Binding CustomTitleText}" MaxLength="80"
 Width="150"
 Grid.ColumnSpan="3"/>

The problem lies in the style's trigger condition

<Condition Property="Text"  Value="{x:Null}" />

It wont work whenever my CustomTitleText property is null, When I changed my style trigger condition to the empty string

<Condition Property="Text"  Value="" />

it worked fine for the null as it considered null as empty string but I dont want that. I don't understand why its not considering null as a null in the trigger condition.

I'm eagerly waiting for your suggestion, Thanks in advance.