Silverlight 2: XamlParseException in Silverlight 2

Question

I have the following problem that appears in Silverlight 2; in Silverlight 3 the same code works OK.

The XAML code is the following:

<UserControl x:Class="My_Discussions.ThreadListItem"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
xmlns:vsm="clr-namespace:System.Windows;assembly=System.Windows"
xmlns:discussion="clr-namespace:My_Discussions"
Width="Auto" Height="Auto">       

<UserControl.Resources>

    <ControlTemplate x:Key="TopicItem">
        <Grid x:Name="TopicItemHost" ShowGridLines="False" Margin="0,8" VerticalAlignment="Stretch">
            <vsm:VisualStateManager.VisualStateGroups>
                <vsm:VisualStateGroup x:Name="CommonStates">
                    <vsm:VisualState x:Name="Normal" />
                    <vsm:VisualState x:Name="MouseOver">
                        <Storyboard>
                            <DoubleAnimation 
                                    Storyboard.TargetName="hotRect" 
                                    Storyboard.TargetProperty="Opacity"
                                    Duration="0"
                                    To="1" />
                            <ObjectAnimationUsingKeyFrames 
                                Storyboard.TargetName="TopicItemHost" 
                                Storyboard.TargetProperty="Cursor" 
                                Duration="0">
                                <DiscreteObjectKeyFrame KeyTime="0">
                                    <DiscreteObjectKeyFrame.Value>
                                        <Cursors>Hand</Cursors>
                                    </DiscreteObjectKeyFrame.Value>
                                </DiscreteObjectKeyFrame>
                            </ObjectAnimationUsingKeyFrames>
                        </Storyboard>
                    </vsm:VisualState>
                </vsm:VisualStateGroup>
                <vsm:VisualStateGroup x:Name="FocusStates">
                    <vsm:VisualState x:Name="Unfocused" />
                    <vsm:VisualState x:Name="Focused">
                        <Storyboard>
                            <DoubleAnimation 
                                    Storyboard.TargetName="focusRect" 
                                    Storyboard.TargetProperty="Opacity"
                                    Duration="0"
                                    To="1" />
                        </Storyboard>
                    </vsm:VisualState>
                </vsm:VisualStateGroup>
                <vsm:VisualStateGroup x:Name="ReadUnreadStates">
                    <vsm:VisualState x:Name="Read" />
                    <vsm:VisualState x:Name="Unread">
                        <Storyboard>
                            <ObjectAnimationUsingKeyFrames 
                                Storyboard.TargetName="TopicTitle" 
                                Storyboard.TargetProperty="FontWeight" 
                                Duration="0">
                                <DiscreteObjectKeyFrame KeyTime="0">
                                    <DiscreteObjectKeyFrame.Value>
                                        <FontWeight>Bold</FontWeight>
                                    </DiscreteObjectKeyFrame.Value>
                                </DiscreteObjectKeyFrame>
                            </ObjectAnimationUsingKeyFrames>
                        </Storyboard>
                    </vsm:VisualState>
                </vsm:VisualStateGroup>
            </vsm:VisualStateManager.VisualStateGroups>

            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto" MinWidth="10"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>

            <Rectangle x:Name="focusRect" Grid.Column="0" Grid.ColumnSpan="3" Grid.RowSpan="2" Fill="#F0F0F0" Margin="0,-8"  Opacity="0"/>
            <Rectangle x:Name="hotRect" Grid.Column="1" Height="1" Margin="0,0,0,0" VerticalAlignment="Bottom" Opacity="0"
                       >
                <Rectangle.Fill>
                    <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
                        <GradientStop Color="#4080C0" Offset="0" />
                        <GradientStop Color="Gray" Offset="0.5" />
                        <GradientStop Color="White" Offset="1" />
                    </LinearGradientBrush>
                </Rectangle.Fill>
            </Rectangle>

            <Image x:Name="TopicLock" Grid.Column="0" Visibility="Collapsed" 
                   Stretch="None" Source="Images/locked.png" Margin="10,2,10,0" 
                   VerticalAlignment="Top" />

            <discussion:ThreadListItemTitleHost Grid.Column="1" 
                                                HorizontalAlignment="Left"
                                                VerticalAlignment="Stretch">
                <discussion:TextCut x:Name="TopicTitle" 
                                    Padding="0,0" 
                                    Foreground="#4080C0" 
                                    HorizontalAlignment="Left"
                                    VerticalAlignment="Top"/>

                <discussion:TextCut x:Name="TopicBody"  
                                    Padding="4,0" 
                                    VerticalAlignment="Top"
                                    HorizontalAlignment="Left"
                                    Foreground="Gray"/>
            </discussion:ThreadListItemTitleHost>

        </Grid>
    </ControlTemplate>

    <ControlTemplate x:Key="ProjectItem">
        <TextBlock x:Name="Project" Padding="10,8" VerticalAlignment="Top" TextWrapping="Wrap"/>
    </ControlTemplate>

    <ControlTemplate x:Key="MessagesItem">
        <TextBlock x:Name="Messages" Padding="10,8" VerticalAlignment="Top"/>
    </ControlTemplate>

    <ControlTemplate x:Key="AuthorItem">
        <discussion:TextCut x:Name="Author" Padding="10,8" VerticalAlignment="Top" HorizontalAlignment="Stretch"/>
    </ControlTemplate>

    <ControlTemplate x:Key="DateItem">
        <TextBlock x:Name="Date" Padding="10,8" VerticalAlignment="Top" />
    </ControlTemplate>

    <ControlTemplate x:Key="BottomBorder">
        <Rectangle Width="Auto" Height="0.5" VerticalAlignment="Bottom" Stroke="Gray" StrokeThickness="0.5" />
    </ControlTemplate>

</UserControl.Resources>

So, there is a control named "TopicTitle" in the XAML. Class TextCut that implements the control contains property "FontWeight":

public static readonly DependencyProperty FontWeightProperty = DependencyProperty.RegisterAttached(
        "FontWeight", 
        typeof(FontWeight), 
        typeof(TextCut),
        new PropertyMetadata(new PropertyChangedCallback(OnFontWeightPropertyChanged)));

Then I call "VisualStateManager.GoToState(ctrl, "Unread", false)". This call should set value Bold into property "FontWeight" of the control "TopicTitle".

On Silverlight 2.0 the following exception happens:

XamlParseException: LineNumber: 0 LinePosition: 0 Message: "[Line:0 Position:0]" The call stack was: MS.Internal.XcpImports.CheckHResult(UInt32 hr) at MS.Internal.XcpImports.Storyboard_SeekAlignedToLastTick(Storyboard storyboard, Single seekTime) at System.Windows.Media.Animation.Storyboard.SeekAlignedToLastTick(TimeSpan offset) at System.Windows.VisualStateGroup.StartNewThenStopOld(FrameworkElement element, Storyboard[] newStoryboards) at System.Windows.VisualStateManager.GoToStateInternal(Control control, FrameworkElement element, VisualStateGroup group, VisualState state, Boolean useTransitions) at System.Windows.VisualStateManager.GoToState(Control control, String stateName, Boolean useTransitions)

On Silverlight 3.0, as I said, there are no problems. The question is: what happens on Silverlight 2.0 and how can avoid this? What is the "[Line:0 Position:0]" - it tells nothing to me.

Answer 1

Well my Silverlight 2 knowledge is quite rusty but looking at the call stack I'd say its getting upset by this:-

<FontWeight>Bold</FontWeight>

I'm sure you must have good reasons for sticking with SL2 but I can't help stating that may be the fix is to use SL3.