How converter null to ImageNull.jpg

This code not work? column don't show

<sdk:DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                    <Image Tag="{Binding photo}" MaxHeight="50">
                                        <Image.Source>
                                            <BitmapImage UriSource="{Binding photo, Converter={StaticResource ConvertNullImageKey}}" />
                                        </Image.Source>
                                    </Image>
                                </DataTemplate>
                        </sdk:DataGridTemplateColumn.CellTemplate>

Converter:

public class ConvertNullImage : IValueConverter
       开发者_开发技巧 {

            public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
            {
                var image = new BitmapImage();
                try
                {
                    image = new BitmapImage(new Uri(value.ToString()));
                    return image;
                }
                catch { return new BitmapImage(new Uri("http://upload.wikimedia.org/wikipedia/commons/1/1c/No-Symbol.png")); }
            }

            public object ConvertBack(object value, Type targetType, object parameter,
                                      CultureInfo culture)
            {
                throw new NotImplementedException();
            }
        }

What you are currently doing is taking an existing BitmapImage and trying to assign another BitmapImage to its UriSource. Have you tried this:-

<Image Tag="{Binding photo}" MaxHeight="50" Source="{Binding photo, Converter={StaticResource ConvertNullImageKey}}" />