WPF IValueConverter for DateTime grid field - wpf

Question

I have a xamDataGrid where I read in data from a file. This field is of type datetime. I would like to change the foreground color of this column when the date loaded is greater than todays date. I have a following IValueConverter:
public class MyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value != null)
{
var color = new SolidColorBrush(Colors.Red);
int result = DateTime.Compare((DateTime)value, todaysDate);
if (result > 0)
return color = new SolidColorBrush(Colors.Red);
else
return color = new SolidColorBrush(Colors.White);
}
return Binding.DoNothing;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
I get and error from this: (DateTime)value
When I step through the code it seems that the if (value !=null) is executed even though there is no data being displayed in the datagrid. Not sure why this is in this path. It should only be executed when I'm loading a file into the datagrid.
Here is the xaml:
<viewModel:MyConverter x:Key="myDateConv"/>
<igDP:UnboundField Name="My Date" BindingPath="MyDate" Width="Auto" BindingMode="TwoWay" >
<igDP:UnboundField.Settings>
<igDP:FieldSettings AllowEdit="True" >
<igDP:FieldSettings.EditorStyle>
<Style TargetType="{x:Type igEditors:XamDateTimeEditor}" >
<Setter Property="Mask" Value="mm/dd/yyyy" />
<Setter Property="Foreground" Value="{Binding RelativeSource={x:Static RelativeSource.Self},Converter={StaticResource myDateConv}}"/>
</Style>
</igDP:FieldSettings.EditorStyle>
</igDP:FieldSettings>
</igDP:UnboundField.Settings>
</igDP:UnboundField>
here is the class:
public class myPrice : INotifyPropertyChanged
{
private DateTime myDate;
public DateTime MyDate
{
get { return myDate; }
set
{
if (myDate != value)
{
priceDate = value;
NotifyPropertyChanged("MyDate");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(string propName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}