Join with specific array index in c# code example

Example 1: c# join string array

var combined = String.Join(",", new String[]{"a","b"});
// a,b

Example 2: c# array.join

String Array...
AB
BC
CD
DE
EF
FG
GH
IJ
Result (after joining) = AB*BC*CD*DE*EF*FG*GH*IJ