[WPF] Error in Design Mode

Hi,

In my UserControl I added:

private void UserControl_Loaded(object sender, RoutedEventArgs e)
{
	if (LicenseManager.UsageMode != LicenseUsageMode.Designtime)
	{
		if (_operation.Equals(Definition.SampleDetailOperation.Insert))
		{
			if(DomainData.GetApplicationVar(ApplicationVars.SmplDefaultPriority) != null)
			{
				cmbSamplePriority.SelectedValue = DomainData.GetApplicationVar(ApplicationVars.SmplDefaultPriority).Value;
			}
		}
	}
}

In RunTime mode the application works, but in DesignMode there is this error:

Microsoft.Practices.ObjectBuilder2.BuildFailedException
The current build operation (build key Build Key[Microsoft.Practices.EnterpriseLibrary.Data.Database, null]) failed: The value can not be null or an empty string. (Strategy type Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ObjectBuilder.ConfiguredObjectStrategy, index 2)

in particular the error is on:
if (DomainData.GetApplicationVar(ApplicationVars.SmplDefaultPriority) != null)

Isn't correct the check:

if (LicenseManager.UsageMode != LicenseUsageMode.Designtime)
{
	//TODO
}

?

Thanks.