WPF Learn： Brush

LineBrush:

<Rectangle Height="145" HorizontalAlignment="Left"  Name="ellipse2" Stroke="Black" VerticalAlignment="Top" Width="301" >
            <Rectangle.Fill>
                <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
                    <GradientStop Color="Black" Offset="0"></GradientStop>
                    <GradientStop Color="Red" Offset="1"></GradientStop>
                </LinearGradientBrush>
            </Rectangle.Fill>
        </Rectangle>

RadialGradientBrush:

<Rectangle Width="200" Height="200" Margin="12,365,340,122">
            <Rectangle.Fill>
                <RadialGradientBrush GradientOrigin="0.8,0.8">
                    <GradientStop Color="White" Offset="0">
                    </GradientStop>

                    <GradientStop  Color="Black" Offset="1">
                    </GradientStop>
                </RadialGradientBrush>
            </Rectangle.Fill>
        </Rectangle>

<Ellipse Width="200" Height="200" Margin="12,159,340,328">
            <Ellipse.Fill>
                <RadialGradientBrush>
                    <GradientStop Color="White" Offset="0">
                    </GradientStop>

                    <GradientStop  Color="Black" Offset="1">
                    </GradientStop>
                </RadialGradientBrush>
            </Ellipse.Fill>
        </Ellipse>

Result: