Multidatatrigger vs datatrigger. Why does my multidatatrigger not work?

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I cannot figure out why this does not work:

HTML

<resourcedictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style x:Key="Brush_GridBackground" TargetType="{x:Type Grid}">
        <Style.Triggers>
            <multidatatrigger>
                <multidatatrigger.conditions>
                    <condition binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="Red" />
                    <condition binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="White" />
                    <condition binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="Black" />
                    <condition binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="Blue" />
                    <condition binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="Green" />
                </multidatatrigger.conditions>
                <setter property="Background" value="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" />
            </multidatatrigger>
        </Style.Triggers>
    </Style>
</resourcedictionary>

When this works:

HTML

<resourcedictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style x:Key="Brush_GridBackground" TargetType="{x:Type Grid}">
        <Style.Triggers>
                <datatrigger binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="Red">
                <setter property="Background" value="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" />
            </datatrigger>
            <datatrigger binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="White">
                <setter property="Background" value="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" />
            </datatrigger>
            <datatrigger binding="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" value="Black">
                <setter property="Background" value="{Binding ElementName=cb_BackgroundColor, Path=SelectedItem.Tag}" />
            </datatrigger>
        </Style.Triggers>
    </Style>
</resourcedictionary>

Posted 7-Oct-11 6:57am

ErikSvendsen

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Simon Bang Terkildsen · Accepted Answer · 2011-10-07T08:53:00

The conditions in your MultiDataTrigger are and'ed together thus all has to be true, which is not possible in the posted example.
While in the DataTrigger example all the DataTrigger's gets evaluated and any that is true gets to set values.

So multiple triggers are or'ed together, if they set the save value the last one on the list gets it's way. And the type of trigger called MultiDataTrigger/MultiTrigger has a collection of conditions which must all be evaluated to true for the trigger to set any value(s).