Extruding curve and editing non destructively How would the following be possible using Blender? The example image is from Cinema 4D where this is easy. The shape is made with one spline of which two instances are made and set as children for the extrude modifier.

I have a curve, which is extruded into two different parts. The two parts are mainly needed because I need to different textures for the different surfaces ("Top" and "Side" in the example).

I tried to use the curve's bevel/extrude options in Blender and can get about this shape, while still maintaining the object as a curve (ie. not transforming to mesh). But how can I apply different textures to the different sides?

The main point of this exercise is to keep the curve editable, so that the extrusions follow the editing (if I convert to a mesh I can't easily change the shape of the curve for the surfaces afterwards).
I don't think you can directly assign two different textures to a curve.
But as a workaround, you can use a Gradient texture.

I'm just mixing two colors, but you can mix any number of shaders/textures...