How can I draw a "soft" line in WPF (presumably using a LinearGradientBrush)?

Try to use a shape instead of a line

<Path Data="M0,0 L25,25 z" Fill="#FFF4F4F5" StrokeThickness="5" Canvas.Left="122" Canvas.Top="58">
<Path.Stroke>
    <LinearGradientBrush EndPoint="1.135,0.994" StartPoint="-0.177,-0.077">
        <GradientStop Color="Black"/>
        <GradientStop Color="#FF68A8FF" Offset="1"/>
    </LinearGradientBrush>
</Path.Stroke>

Tomer

Well, I do not know if that is applicable to your scenario but you could simply rotate the horizontal line using LayoutTransform and the gradient will be okay.

<Line   HorizontalAlignment="Stretch" VerticalAlignment="Center"
    Stretch="Uniform" StrokeThickness="5" X1="0" Y1="0" X2="1" Y2="0">
<Shape.Stroke>
    <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
        <GradientStop Color="Transparent" Offset="0" />
        <GradientStop Color="Green" Offset="0.5" />
        <GradientStop Color="Transparent" Offset="1" />
    </LinearGradientBrush>
</Shape.Stroke>
    <Line.LayoutTransform>
        <RotateTransform Angle="40"/>
    </Line.LayoutTransform>