I've started styling my non-Infragistics WPF controls using MS Controls Implicit Themes.

However, I get the error message 'Object reference not set to an instance of an object' in the XAML designer when I use a regular WPF ComboBox and set IsEditable="True". The build actually succeeds and my applications runs, but the error is still reported. If I remove the IG resource dictionary then the error goes away.

I also get a similar error when I use XamComboEditor while using MS Control Implicit Themes.

Any help you can provide is appreciated.

Here's a simplified version of my XAML.

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:ig="http://schemas.infragistics.com/xaml"
        xmlns:igDP="http://schemas.infragistics.com/xaml/wpf"         
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="691" Width="1229" >
    
    <Grid>
        <Grid.Resources>
            <ResourceDictionary Source="Themes/Office2010Blue/Office2010Blue.MSControls.Core.Implicit.xaml" />
        </Grid.Resources>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <ComboBox Grid.Row="0" IsEditable="True" />   
        <ig:XamComboEditor Grid.Row="1" />
    </Grid>
</Window>

Thank You