Select connecting edges

I am working on a 3d modelling app, I have achieved vertex, face and edge selection. But want to be able to select connected edges when I double tap on an edge, any ideas?
I can share my code in pm

something like this
EveryOtherLoop

What is/are (a) connected edge(s) of an edge? I don’t quite understand the link with your 3rd picture.

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I mean multi selecting edge loop

I guess you will need to build a structure that will let you find edges adjacent to other edges. See for eg flipcode - The Half-Edge Data Structure