Datatrigger on empty string

Question

How can a DataTrigger change the visibility of stackpanel, based on a binded string? I have the following Xaml

<StackPanel HorizontalAlignment="Right" 
            Orientation="Horizontal" 
            Grid.Column="1"
            Background="#FF7a7a7a">
    <StackPanel.Style>
        <Style TargetType="{x:Type StackPanel}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding SearchText}" Value="">
                    <Setter Property="Visibility" Value="Hidden"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </StackPanel.Style>
    Content....
   </StackPanel>

I Know that SearchText gets updates and binds properly outside the StackPanel

Could somebody point me in the right direction?

When I bind to a TextBoxText property it works. Do you know what your property is returning? — trinaldi
– trinaldi, Commented Oct 7, 2013 at 22:58
Yes, but is it returning any value or is it returning null — trinaldi
– trinaldi, Commented Oct 7, 2013 at 23:03

Fede · Accepted Answer · 2013-10-07 22:55:21Z

46

This:

<DataTrigger Binding="{Binding SearchText}" Value="">
   <Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>

will work for empty string (""), however it will not work for null.

Add another DataTrigger for the null case:

<DataTrigger Binding="{Binding SearchText}" Value="{x:Null}">
   <Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>

answered Oct 7, 2013 at 22:55

Fede

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1 Comment

Bryan Over a year ago

You can combine both triggers into one if you add the following as part of the binding expression TargetNullValue=''

Buzzy · Accepted Answer · 2016-02-26 10:00:06Z

16

Correct using String.Empty in XAML:

xmlns:sys="clr-namespace:System;assembly=mscorlib"
...
<DataTrigger Binding="{Binding SearchText}" Value="{x:Static sys:String.Empty}">

answered Feb 26, 2016 at 10:00

Buzzy

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Comments

trinaldi · Accepted Answer · 2013-10-07 23:01:27Z

0

Weird as it might sound, the code below works for me:

<StackPanel Background="#FF7a7a7a">
    <StackPanel.Style>
        <Style TargetType="{x:Type StackPanel}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Text, ElementName=textBlock}" Value="">
                    <Setter Property="Visibility" Value="Hidden"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </StackPanel.Style>
    <TextBox x:Name="textBlock" Text="" Width="100" Height="30"></TextBox>
</StackPanel>

Can you tell the value your Property is sending?

answered Oct 7, 2013 at 23:01

trinaldi

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2 Comments

Giffesnaffen Over a year ago

The my string was not initialized having a value of null, therefor it seemed to not work.

trinaldi Over a year ago

Yeah, @HighCore was spot on!

Rahul Misra · Accepted Answer · 2013-10-07 23:08:47Z

0

Try this

<StackPanel.Style>
                                        <Style TargetType="StackPanel">
                                            <Setter Property="Visibility" Value="Collapsed"/>
                                            <Style.Triggers>
                                                <DataTrigger Binding="{Binding YourBoundPropertyName}" Value="True">
                                                    <Setter Property="Visibility" Value="Visible"/>

                                                </DataTrigger>
                                            </Style.Triggers>
                                        </Style>
                                    </StackPanel.Style>

answered Oct 7, 2013 at 23:08

Rahul Misra

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