SL4.文本渐变

 <TextBlock Text="文字正在渐变" FontFamily="Arial" FontSize="56">
            <TextBlock.Foreground>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="Green"></GradientStop>
                    <GradientStop Color="Blue" Offset="1"></GradientStop>
                </LinearGradientBrush>
            </TextBlock.Foreground>
        </TextBlock>