This should work:
<TextBox Text="{Binding Model.DisplayName.Value}" Height="28" HorizontalAlignment="Left" Name="title_TB" VerticalAlignment="Top" Width="Auto" FontWeight="Bold" FontSize="14" Margin="5,2,0,0" />
And, update Value property to have setter:
private string _thisShouldBeAValidField ;
public string Value
{
get
{
if(_thisShouldBeAValidField!=null) return _thisShouldBeAValidField;
var sb = new StringBuilder();
if (_nestedMultiItemStrings)
{
foreach (var MultiItemString in _nestedItems)
{
sb.Append(MultiItemString.Value);
}
}
else
{
foreach (var key in _keys)
{
sb.Append(_resourceKey ? (string)Application.Current.Resources[key] : key);
}
}
return sb.ToString();
}
set{
_thisShouldBeAValidField = value;
}
}