Hello,

I have a custom base user control in silverlight.

<UserControl x:Class="Problemo.MyBaseControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White">
        <Border Name="HeaderControl" Background="Red" />
    </Grid>
</UserControl>

With the following code behind

public partial class MyBaseControl : UserControl
    {
        public UIElement Header { get; set; }

        public MyBaseControl()
        {
            InitializeComponent();
            Loaded += MyBaseControl_Loaded;
        }

        void MyBaseControl_Loaded(object sender, RoutedEventArgs e)
        {
            HeaderControl.Child = Header;
        }
    }

I have a derived control.

<me:MyBaseControl x:Class="Problemo.MyControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    xmlns:me="clr-namespace:Problemo" 
    d:DesignHeight="300" d:DesignWidth="400">
    <me:MyBaseControl.Header>
        <TextBlock Name="header" Text="{Binding Text}" />
    </me:MyBaseControl.Header> 
</me:MyBaseControl>

With the following code behind.

 public partial class MyControl : MyBaseControl
    {
        public string Text
        {
            get; set;
        }

        public MyControl(string text)
        {
            InitializeComponent();
            Text = text;
        }
    }

I'm trying to set the text value of the header textblock in the derived control.

It would be nice to be able to set both ways, i.e. with databinding or in the derived control code behind, but neither work. With the data binding, it doesn't work. If I try in the code behind I get a null reference to 'header'. This is silverlight 4 (not sure if that makes a difference)

Any suggestions on how to do with with both databinding and in code ?

Cheers