<DataGrid IsReadOnly="True" AutoGenerateColumns="False" Background="#2D2D30" x:Name="dgSearch" ItemsSource="{Binding BookingsModel.Bookings, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}">

   <DataGridTemplateColumn Header="Show Informations">
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <Button Style="{StaticResource Flat}" Command="{Binding Path=OpenSingleBookingInfo, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type vm:MoneyModel}}}" CommandParameter="{Binding ElementName=dgOverview, Path=SelectedItem.ID}">
                                    <Image Source="\images\Ok-icon.png" Width="16" Height="16"/>
                                </Button>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                </DataGrid.Columns>

                                            <i:InvokeCommandAction Command="{Binding Mode=TwoWay, Path=Bookings, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type vm:Money}}}" CommandParameter="{Binding ElementName=dgOverview, Path=SelectedItem.ID}"/>

       <i:Interaction.Triggers>
                                        <i:EventTrigger EventName="Click">
                                            <i:InvokeCommandAction Command="{Binding RelativeSource={RelativeSource AncestorType=Page, Mode=FindAncestor}, Path=DataContext.Buchungen.OpenSingleBookingInfo }" CommandParameter="{Binding ElementName=dgSearch, Path=SelectedItem}" />
                                        </i:EventTrigger>
                                    </i:Interaction.Triggers>

/// <summary> Bindet den DataContext gegen Elemente, die nicht im Visual-Tree auftauchen </summary>
public sealed class DataContextBinder : Freezable
{
    /// <summary> Dependency-Property von <see cref="DataContext"/> </summary>
    public static readonly DependencyProperty DataContextProperty =
        DependencyProperty.Register(nameof(DataContext),
            typeof(object),
            typeof(DataContextBinder),
            new PropertyMetadata(null));

    /// <summary> zu bindende DataContext </summary>
    public object DataContext
    {
        get { return GetValue(DataContextProperty); }
        set { SetValue(DataContextProperty, value); }
    }

    /// <summary> Erzeugt eine neue Instanz von <see cref="DataContextBinder"/> </summary>
    protected override Freezable CreateInstanceCore()
        => new DataContextBinder();
}

<Window.Resources>
    <utils:DataContextBinder x:Key="DataContextBinder" DataContext="{Binding}"/>
</Window.Resources>

<DataTemplate>
    <TextBox Text="{Binding Source={StaticResource DataContextBinder}, Path=DataContext.TextProperty}"  />
</DataTemplate>