binding to static property problem

I'm using the EntityFramework and working on an invoicing application. Below is the xaml code from myDataGrid. Now it compiles and everything works great, but the problem is, the static binding I have on the DataGridComboBoxColumn throws an exception when in designer mode because that static property actually loads from a MySql database using the entity framework.

    <DataGrid x:Name="ItemsGrid" Grid.Row="2" Grid.ColumnSpan="3" ItemsSource="{Binding Items}" FontSize="11" AutoGenerateColumns="False" CanUserAddRows="False" RowHeaderWidth="0" GridLinesVisibility="None" CanUserResizeRows="False" CanUserResizeColumns="False" CanUserReorderColumns="False">
        <DataGrid.Columns>
            <DataGridTemplateColumn Width="150" Header="Item No.">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <TextBox Width="130" BorderThickness="0" Background="Transparent" Text="{Binding Number}" />
                            <Image MouseDown="ItemSelectionButton_Click" Margin="0,0,0,0" Width="12" Source="/Images/Icons/SearchBlack.png" />
                        </StackPanel>
                    </Data开发者_运维技巧Template>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
            <DataGridTextColumn Width="70" Header="Quantity" Binding="{Binding Quantity}" />
            <DataGridTextColumn Width="70" Header="Order" Binding="{Binding Order}" />
            <DataGridTextColumn Width="70" Header="B/O" Binding="{Binding BackOrder}" />
            <DataGridTextColumn Width="60" Header="Units" Binding="{Binding Units}" />
            <DataGridTextColumn Width="200" Header="Description" Binding="{Binding Description}" />
            <DataGridTextColumn Width="90" Header="Price" Binding="{Binding Price}" />
            <DataGridComboBoxColumn Width="50" Header="Tax" ItemsSource="{x:Static app:Session.TaxCodes}" SelectedValueBinding="{Binding TaxCodeID}" DisplayMemberPath="Code" SelectedValuePath="ID" />
            <DataGridTextColumn Width="90" Header="Amount" Binding="{Binding Amount}" />
            <DataGridTextColumn Width="90" Header="Linked" Binding="{Binding SalesOrderID}" />
        </DataGrid.Columns>
    </DataGrid>

Here's the exception:

The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid.
   at System.Data.EntityClient.EntityConnection.ChangeConnectionString(String newConnectionString)
   at System.Data.EntityClient.EntityConnection..ctor(String connectionString)
   at System.Data.Objects.ObjectContext.CreateEntityConnection(String connectionString)
   at System.Data.Objects.ObjectContext..ctor(String connectionString, String defaultContainerName)
   at DtcInvoicer.Models.DatabaseEntities..ctor() in F:\Development\DTC Industrial\DtcInvoicer\DtcInvoicer\Models\DatabaseModel.Designer.cs:line 42
   at DtcInvoicer.Models.Repository.get_GetContext() in F:\Development\DTC Industrial\DtcInvoicer\DtcInvoicer\Models\Repository.cs:line 14
   at DtcInvoicer.Models.TaxCodesRepository.SelectAll() in F:\Development\DTC Industrial\DtcInvoicer\DtcInvoicer\Models\TaxCodesRepository.cs:line 54
   at DtcInvoicer.Session..cctor() in F:\Development\DTC Industrial\DtcInvoicer\DtcInvoicer\Session.cs:line 18

I know trying to fix the root of the problem will be too much work, I'm wondering if there's a simple workaround like dynamically binding to a static property in another class. Anyone have any idea how to do this? Looking for a xaml only solution.

Here's what I already tried...

ItemsSource="{Binding Path=TaxCodes, Source={x:Static app:Session}}"

ItemsSource="{Binding Path=TaxCodes, Source={StaticResource app:Session}}"

ItemsSource="{Binding app:Session.TaxCodes}"

Any help is appreciated.

Thanks.

Could you use something like d:ItemsSource="{x:Null}", and define d in your Window or UserControl like mc:Ignorable="d"?

It should make the design-time property of ItemsSource equal to null

Edit

Forgot to add the definition for mc - It is xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"