To make solid from surface (17.4 KB)
loft-sweep2.3dm (166.8 KB)
I want to make solid in two ways
but It is weird results.

Thank you~!

sounds trivial but there is a lot of help in there:
do it manually and you see how you need to do it in grasshopper.

Sweep and loft is not how you do it.
Simply offset and connect edges,
If your shape is of low curvature, it might also a better idea to translate it in average normal direction in order to prevent real offsetting. Offsetting is not trivial and in 99 % of all cases your curved surface gets higher in cp count. So cp reduction is beneficial but not mandatory.

Pufferfish has an offset surface component that can do both sides and as solid.

Thank you so much Mr. Michael Pryor ^^