Windows Phone 設置畫刷

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>
            <!--這裏是用畫刷來設置對角線漸變-->
            <TextBlock Grid.Row="0" HorizontalAlignment="Left" FontSize="50" Text="對角線漸變" TextWrapping="Wrap">
                <TextBlock.Foreground>
                    <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
                        <GradientStop Color="Silver" Offset="0"/>
                        <GradientStop Color="Gold" Offset="0.38"/>
                        <GradientStop Color="Orange" Offset="0.55"/>
                        <GradientStop Color="DarkBlue" Offset="1"/>
                    </LinearGradientBrush>
                </TextBlock.Foreground>
            </TextBlock>
            
            <TextBlock Grid.Row="1" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="65" TextWrapping="Wrap" Text="徑向漸變">
                <TextBlock.Foreground>
                    <RadialGradientBrush>
                        <GradientStop Color="#ff4199b6" Offset="0.1"/>
                        <GradientStop Color="#ff3f2bed" Offset="0.45"/>
                        <GradientStop Color="#fff0e1f5" Offset="0.78"/>
                        <GradientStop Color="#ff55ea1a" Offset="1"/>
                    </RadialGradientBrush>
                </TextBlock.Foreground>
            </TextBlock>
            
            <TextBlock Grid.Row="2" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="50" TextWrapping="Wrap" Text="垂直方向漸變" >
                <TextBlock.Foreground>
                    <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
                        <GradientStop Color="#fff2ede3" Offset="0"/>
                        <GradientStop Color="#ffd53d52" Offset="1"/>
                    </LinearGradientBrush>
                </TextBlock.Foreground>
            </TextBlock>
            
            <TextBlock Grid.Row="3" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="50" TextWrapping="Wrap" Text="不在中心的徑向漸變" >
                <TextBlock.Foreground>
                    <RadialGradientBrush Center="0.5,1" RadiusY="1">
                        <GradientStop Color="Red" Offset="0"/>
                        <GradientStop Color="Orange" Offset="0.25"/>
                        <GradientStop Color="Yellow" Offset="0.5"/>
                        <GradientStop Color="Green" Offset="0.75"/>
                        <GradientStop Color="Blue" Offset="1"/>
                    </RadialGradientBrush>
                </TextBlock.Foreground>
            </TextBlock>            
        </Grid>