So far I've been able to produce dashes on an undirected edge:
Graph[{1 -> 2, 3 \[UndirectedEdge] 1, 3 \[UndirectedEdge] 2},
EdgeStyle -> {3 \[UndirectedEdge] 1 -> Dashed}, VertexLabels -> All,
ImageSize -> Small]
a bidirectional edge:
Graph[{1 \[UndirectedEdge] 2, 3 <-> 1, 3 \[UndirectedEdge] 2},
EdgeStyle -> {3 <-> 1 -> Dashed}, VertexLabels -> All,
ImageSize -> Small]
But not a single-directed edge:
Graph[{1 \[UndirectedEdge] 2, 3 -> 1, 3 \[UndirectedEdge] 2},
EdgeStyle -> {3 -> 1 -> Dashed}, VertexLabels -> All,
ImageSize -> Small]
(FAILS)
Thank you in advance :-)