Hello. I'm getting a weird error and I have no idea why. Here is my setup:

I put the XamMultiColumnComboEditor into a field in my xamdatagrid.

<Style x:Key="VGStatusCodesStyle" TargetType="{x:Type igWPF:XamTextEditor }">
<Setter Property="EditTemplate">
<Setter.Value>
<ControlTemplate>
<ig:XamMultiColumnComboEditor Name="VGStatusCodes"
ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}},
Path=DataContext.ValveGroupStatusCodes}"

DisplayMemberPath="StatusCode"
SelectedValuePath="StatusCode"
Width="80"

SelectedItem="{Binding RelativeSource={RelativeSource TemplatedParent},
Path=Value, Mode=TwoWay,
Converter={StaticResource StatusCodesToStringConverter}}"

MaxDropDownWidth="275"
MaxDropDownHeight="270">

</ig:XamMultiColumnComboEditor>
</ControlTemplate>
</Setter.Value>
</Setter>

public class StatusCodesToStringConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return Binding.DoNothing;
}

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is ValveGroupStatusCode)
return (value as ValveGroupStatusCode).StatusCode;

return Binding.DoNothing;
}
}

in the view model I'm handling the EditModeEnded and CellChanged event for the xamdatagrid. So if someone pics a particular row from the XamMultiColumnComboEditor I have to delete that row automatically Sequence of events:

1.The CellChanged event executes and in it I call the end edit mode method ->e.Cell.EndEditMode();

2. The code goes into the EditModeEnded method and here is where I want to delete the row whos cell changed:

var ID = e.Cell.Record.Cells[0].Value;

LogData.Rows.Find(ID).Delete(); //LogData is bound to my xamdatagrid, it's a DataTable

If I do all this on a small test project I set up, everything works fine. But it does not in my main project. I can't seem to reproduce the problem. 

I traced the issue to this in the style

SelectedItem="{Binding RelativeSource={RelativeSource TemplatedParent}, 
Path=Value, Mode=TwoWay, 
Converter={StaticResource StatusCodesToStringConverter}}"

So if I take this code away the row get deleted without issue else I get this error:

Internal error: internal WPF code tried to reactivate a BindingExpression that was already marked as detached. 

System.Windows.Data Error: 8 : Cannot save value from target back to source. BindingExpression:Path=Value; DataItem=null;  NullReferenceException:'System.NullReferenceException: Object reference not set to an instance of an object

Why would or what is causing the DataItem be null? --> Path=Value; DataItem=null; 

I wondering you someone might give me a hint or an idea where to look.

Thanks