Generate PropertyDefinition in code

[Amin]

What's wrong with this code???
why binding doesn't work???
Check the attachment.


public class UcMetadataPropertyGrid : RadPropertyGrid
    {
        public UcMetadataPropertyGrid(MetadataCollection col)
        {
            foreach (Metadata data in col)
            {
                PropertyDefinition def = new PropertyDefinition();
                def.DisplayName = data.Name;
                //def.Binding = new Binding("StringValue");
                //def.Binding.Source = data;
                //def.Binding.Mode = BindingMode.TwoWay;
                def.EditorTemplate = CreateEditor(data);
                this.PropertyDefinitions.Add(def);
            }
        }

        private DataTemplate CreateEditor(Metadata metadata)
        {
            var dt = new DataTemplate();
            var textbox = new RadWatermarkTextBox() { Name = "cp" };
            textbox.Text = "{Binding Path=StringValue}";
            var binding = new Binding
            {
                Path = new PropertyPath("StringValue"),
                Mode = BindingMode.TwoWay,
                UpdateSourceTrigger = UpdateSourceTrigger.LostFocus,
                Source = metadata
            };
            textbox.SetBinding(Metadata.StringValueProperty, binding);

            //dt.VisualTree = textbox;
            //dt.Seal();
            return dt;
        }

        private DataTemplate CreateEditor()
        {
            var sb = new StringBuilder();
            sb.Append("<DataTemplate ");
            sb.Append("xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' ");
            sb.Append("xmlns:controls='clr-namespace:Nezam.DigitalVideoArchive.UI.Controls;assembly=Nezam.DigitalVideoArchive.UI' ");
            sb.Append("xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>");
            sb.Append("<Grid>");
            sb.Append(@"<TextBox Text=""{Binding StringValue,Mode=TwoWay}"" />");
            sb.Append("</Grid>");
            sb.Append("</DataTemplate>");
            
            return (DataTemplate)System.Windows.Markup.XamlReader.Parse(sb.ToString());
        }
    }



public MainWindow()
        {
            InitializeComponent();

            MetadataCollection col = new MetadataCollection();

            StringMetadata sm = new StringMetadata();
            sm.Name = "StringMetadata";
            sm.StringValue = "Amin";
            col.Add(sm);

            BoolMetadata bm = new BoolMetadata();
            bm.Name = "BoolMetadata";
            bm.Value = true;
            col.Add(bm);

            GuidMetadata gm = new GuidMetadata();
            gm.Name = "GuidMetadata";
            gm.Value = Guid.NewGuid();
            col.Add(gm);

            DateTimeMetadata dm = new DateTimeMetadata();
            dm.Name = "DateTimeMetadata";
            dm.Value = DateTime.Now;
            col.Add(dm);


            UcMetadataPropertyGrid pg = new UcMetadataPropertyGrid(col);
            //pg.FlowDirection = System.Windows.FlowDirection.RightToLeft;
            this.Grid1.Children.Add(pg);
        }