I am using Telerik RadGridView in my project. I want to show image in column.

                GridViewImageColumn col1 = new GridViewImageColumn();
                col1.Width = 100;
                col1.DataMemberBinding = new Binding("id");
                col1.Header = "PhotoByConverter";
                col1.DataMemberBinding.Converter = new ThumbnailConverter();
                grid.Columns.Add(col1);


                GridViewImageColumn col2 = new GridViewImageColumn();
                col2.Width = 100;
                col2.DataMemberBinding = new Binding("firstName");
                col2.Header = "Person name";
                col2.DataMemberBinding.Converter = new ThumbnailConverter();
                grid.Columns.Add(col2);

                Grid.ItemsSource=DataTable;

First column not wokrs but second works fine. I use Converter for image shown below

    public class ThumbnailConverter : IValueConverter
    {

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
                    IEnumerable<thumbNail> result = from n in thumbnails
                                        where n.personID == value.ToString()
                                        select n;


        if (result != null && result.First().thumbnail != null)
        {
            return result.First().thumbnail.file;
        }
        else
        {
            return null;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new Exception("The method or operation is not implemented.");
    }
   }

I found by id thumbnail of person and set it like data for GridViewImageColumn. I checked with Debuger conveter works properly. I can't undesrtand why it doesn't work. Any ideas?